Causes of Diabetes

National Diabetes Information Clearinghouse

What is diabetes?

Diabetes is a complex group of diseases with 

a variety of causes. People with diabetes 

have high blood glucose, also called high 

blood sugar or hyperglycemia. 

Diabetes is a disorder of metabolism—

the way the body uses digested food for 

energy. The digestive tract breaks down 

carbohydrates—sugars and starches found 

in many foods—into glucose, a form of sugar 

that enters the bloodstream. With the help 

of the hormone insulin, cells throughout the 

body absorb glucose and use it for energy. 

Diabetes develops when the body doesn’t 

make enough insulin or is not able to use 

insulin effectively, or both. 

Insulin is made in the pancreas, an organ 

located behind the stomach. The pancreas 

contains clusters of cells called islets. Beta 

cells within the islets make insulin and 

release it into the blood. 

Liver

Pancreatic islet

Beta cell

Pancreas

Islets within the pancreas contain beta cells, which 

make insulin and release it into the blood.

If beta cells don’t produce enough insulin, 

or the body doesn’t respond to the insulin 

that is present, glucose builds up in the 

blood instead of being absorbed by cells in 

the body, leading to prediabetes or diabetes. 

Prediabetes is a condition in which blood 

glucose levels or A1C levels—which reflect 

average blood glucose levels—are higher 

than normal but not high enough to be 

diagnosed as diabetes. In diabetes, the 

body’s cells are starved of energy despite 

high blood glucose levels.

Over time, high blood glucose damages 

nerves and blood vessels, leading to 

complications such as heart disease, stroke, 

kidney disease, blindness, dental disease, 

and amputations. Other complications of 

diabetes may include increased susceptibility 

to other diseases, loss of mobility with aging, 

depression, and pregnancy problems. No 

one is certain what starts the processes that 

cause diabetes, but scientists believe genes 

and environmental factors interact to cause 

diabetes in most cases.

The two main types of diabetes are type 1 

diabetes and type 2 diabetes. A third type, 

gestational diabetes, develops only during 

pregnancy. Other types of diabetes are 

caused by defects in specific genes, diseases 

of the pancreas, certain drugs or chemicals, 

infections, and other conditions. Some 

people show signs of both type 1 and type 2 

diabetes.
2 Causes of Diabetes

What causes type 1 diabetes?

Type 1 diabetes is caused by a lack of insulin 

due to the destruction of insulin-producing 

beta cells in the pancreas. In type 1 

diabetes—an autoimmune disease—the 

body’s immune system attacks and destroys 

the beta cells. Normally, the immune 

system protects the body from infection by 

identifying and destroying bacteria, viruses, 

and other potentially harmful foreign 

substances. But in autoimmune diseases, the 

immune system attacks the body’s own cells. 

In type 1 diabetes, beta cell destruction may 

take place over several years, but symptoms 

of the disease usually develop over a short 

period of time.

Type 1 diabetes typically occurs in children 

and young adults, though it can appear at 

any age. In the past, type 1 diabetes was 

called juvenile diabetes or insulin-dependent 

diabetes mellitus.

Latent autoimmune diabetes in adults 

(LADA) may be a slowly developing kind 

of type 1 diabetes. Diagnosis usually occurs 

after age 30. In LADA, as in type 1 diabetes, 

the body’s immune system destroys the beta 

cells. At the time of diagnosis, people with 

LADA may still produce their own insulin, 

but eventually most will need insulin shots 

or an insulin pump to control blood glucose 

levels. 

Genetic Susceptibility

Heredity plays an important part in 

determining who is likely to develop type 

1 diabetes. Genes are passed down from 

biological parent to child. Genes carry 

instructions for making proteins that are 

needed for the body’s cells to function. 

Many genes, as well as interactions among 

genes, are thought to influence susceptibility 

to and protection from type 1 diabetes. The 

key genes may vary in different population 

groups. Variations in genes that affect more 

than 1 percent of a population group are 

called gene variants.

Certain gene variants that carry instructions 

for making proteins called human leukocyte 

antigens (HLAs) on white blood cells are 

linked to the risk of developing type 1 

diabetes. The proteins produced by HLA 

genes help determine whether the immune 

system recognizes a cell as part of the body 

or as foreign material. Some combinations 

of HLA gene variants predict that a person 

will be at higher risk for type 1 diabetes, 

while other combinations are protective or 

have no effect on risk. 

While HLA genes are the major risk genes 

for type 1 diabetes, many additional risk 

genes or gene regions have been found. Not 

only can these genes help identify people at 

risk for type 1 diabetes, but they also provide 

important clues to help scientists better 

understand how the disease develops and 

identify potential targets for therapy and 

prevention.

Genetic testing can show what types of 

HLA genes a person carries and can reveal 

other genes linked to diabetes. However, 

most genetic testing is done in a research 

setting and is not yet available to individuals. 

Scientists are studying how the results of 

genetic testing can be used to improve type 1 

diabetes prevention or treatment.
3 Causes of Diabetes

Autoimmune Destruction 

of Beta Cells

In type 1 diabetes, white blood cells 

called T cells attack and destroy beta 

cells. The process begins well before 

diabetes symptoms appear and continues 

after diagnosis. Often, type 1 diabetes is 

not diagnosed until most beta cells have 

already been destroyed. At this point, a 

person needs daily insulin treatment to 

survive. Finding ways to modify or stop 

this autoimmune process and preserve beta 

cell function is a major focus of current 

scientific research.

Recent research suggests insulin itself may 

be a key trigger of the immune attack on 

beta cells. The immune systems of people 

who are susceptible to developing type 1 

diabetes respond to insulin as if it were a 

foreign substance, or antigen. To combat 

antigens, the body makes proteins called 

antibodies. Antibodies to insulin and other 

proteins produced by beta cells are found 

in people with type 1 diabetes. Researchers 

test for these antibodies to help identify 

people at increased risk of developing the 

disease. Testing the types and levels of 

antibodies in the blood can help determine 

whether a person has type 1 diabetes, 

LADA, or another type of diabetes.

Environmental Factors

Environmental factors, such as foods, 

viruses, and toxins, may play a role in the 

development of type 1 diabetes, but the exact 

nature of their role has not been determined. 

Some theories suggest that environmental 

factors trigger the autoimmune destruction 

of beta cells in people with a genetic 

susceptibility to diabetes. Other theories 

suggest that environmental factors play 

an ongoing role in diabetes, even after 

diagnosis.

Viruses and infections. A virus cannot 

cause diabetes on its own, but people are 

sometimes diagnosed with type 1 diabetes 

during or after a viral infection, suggesting a 

link between the two. Also, the onset of type 

1 diabetes occurs more frequently during 

the winter when viral infections are more 

common. Viruses possibly associated with 

type 1 diabetes include coxsackievirus B, 

cytomegalovirus, adenovirus, rubella, and 

mumps. Scientists have described several 

ways these viruses may damage or destroy 

beta cells or possibly trigger an autoimmune 

response in susceptible people. For example, 

anti-islet antibodies have been found in 

patients with congenital rubella syndrome, 

and cytomegalovirus has been associated 

with significant beta cell damage and acute 

pancreatitis––inflammation of the pancreas. 

Scientists are trying to identify a virus that 

can cause type 1 diabetes so that a vaccine 

might be developed to prevent the disease.
4 Causes of Diabetes

Infant feeding practices. Some studies have 

suggested that dietary factors may raise or 

lower the risk of developing type 1 diabetes. 

For example, breastfed infants and infants 

receiving vitamin D supplements may have 

a reduced risk of developing type 1 diabetes, 

while early exposure to cow’s milk and cereal 

proteins may increase risk. More research is 

needed to clarify how infant nutrition affects 

the risk for type 1 diabetes. 

Read more in the Centers for Disease 

Control and Prevention’s (CDC’s) 

publication National Diabetes Statistics 

Report, 2014 at www.cdc.gov for 

information about research studies 

related to type 1 diabetes.

What causes type 2 diabetes?

Type 2 diabetes—the most common form 

of diabetes—is caused by a combination 

of factors, including insulin resistance, a 

condition in which the body’s muscle, fat, 

and liver cells do not use insulin effectively. 

Type 2 diabetes develops when the body 

can no longer produce enough insulin to 

compensate for the impaired ability to 

use insulin. Symptoms of type 2 diabetes 

may develop gradually and can be subtle; 

some people with type 2 diabetes remain 

undiagnosed for years.

Type 2 diabetes develops most often in 

middle-aged and older people who are 

also overweight or obese. The disease, 

once rare in youth, is becoming more 

common in overweight and obese children 

and adolescents. Scientists think genetic 

susceptibility and environmental factors are 

the most likely triggers of type 2 diabetes.

Genetic Susceptibility

Genes play a significant part in susceptibility 

to type 2 diabetes. Having certain genes 

or combinations of genes may increase or 

decrease a person’s risk for developing the 

disease. The role of genes is suggested by 

the high rate of type 2 diabetes in families 

and identical twins and wide variations in 

diabetes prevalence by ethnicity. Type 2 

diabetes occurs more frequently in African 

Americans, Alaska Natives, American 

Indians, Hispanics/Latinos, and some Asian 

Americans, Native Hawaiians, and Pacific 

Islander Americans than it does in nonHispanic whites. 

Recent studies have combined genetic data 

from large numbers of people, accelerating 

the pace of gene discovery. Though 

scientists have now identified many gene 

variants that increase susceptibility to 

type 2 diabetes, the majority have yet to be 

discovered. The known genes appear to 

affect insulin production rather than insulin 

resistance. Researchers are working to 

identify additional gene variants and to learn 

how they interact with one another and with 

environmental factors to cause diabetes.

Studies have shown that variants of the 

TCF7L2 gene increase susceptibility to 

type 2 diabetes. For people who inherit two 

copies of the variants, the risk of developing 

type 2 diabetes is about 80 percent higher 

than for those who do not carry the gene 

variant.1 However, even in those with the 

variant, diet and physical activity leading to 

weight loss help delay diabetes, according to 

the Diabetes Prevention Program (DPP), a 

major clinical trial involving people at high 

risk.

1Grant RW, Moore AF, and Florez JC. Genetic 

architecture of type 2 diabetes: recent progress 

and clinical implications. Diabetes Care. 

2009;32(6):1107–1114.
5 Causes of Diabetes

Genes can also increase the risk of diabetes 

by increasing a person’s tendency to become 

overweight or obese. One theory, known 

as the “thrifty gene” hypothesis, suggests 

certain genes increase the efficiency of 

metabolism to extract energy from food and 

store the energy for later use. This survival 

trait was advantageous for populations whose 

food supplies were scarce or unpredictable 

and could help keep people alive during 

famine. In modern times, however, when 

high-calorie foods are plentiful, such a trait 

can promote obesity and type 2 diabetes.

Obesity and Physical Inactivity

Physical inactivity and obesity are strongly 

associated with the development of type 2 

diabetes. People who are genetically 

susceptible to type 2 diabetes are more 

vulnerable when these risk factors are 

present.

An imbalance between caloric intake and 

physical activity can lead to obesity, which 

causes insulin resistance and is common in 

people with type 2 diabetes. Central obesity, 

in which a person has excess abdominal fat, 

is a major risk factor not only for insulin 

resistance and type 2 diabetes but also for 

heart and blood vessel disease, also called 

cardiovascular disease (CVD). This excess 

“belly fat” produces hormones and other 

substances that can cause harmful, chronic 

effects in the body such as damage to blood 

vessels.

The DPP and other studies show that 

millions of people can lower their risk for 

type 2 diabetes by making lifestyle changes 

and losing weight. The DPP proved that 

people with prediabetes—at high risk of 

developing type 2 diabetes—could sharply 

lower their risk by losing weight through 

regular physical activity and a diet low in fat 

and calories. In 2009, a follow-up study of 

DPP participants—the Diabetes Prevention 

Program Outcomes Study (DPPOS)—

showed that the benefits of weight loss lasted 

for at least 10 years after the original study 

began.2

2Diabetes Prevention Program Research Group. 

10-year follow-up of diabetes incidence and weight loss 

in the Diabetes Prevention Program Outcomes Study. 

Lancet. 2009;374(9702):1677–1686.

Read more about the DPP, funded under 

National Institutes of Health (NIH) 

clinical trial number NCT00004992, and 

the DPPOS, funded under NIH clinical 

trial number NCT00038727 in Diabetes 

Prevention Program at www.diabetes.niddk.

nih.gov. 

Insulin Resistance

Insulin resistance is a common condition 

in people who are overweight or obese, 

have excess abdominal fat, and are not 

physically active. Muscle, fat, and liver cells 

stop responding properly to insulin, forcing 

the pancreas to compensate by producing 

extra insulin. As long as beta cells are able 

to produce enough insulin, blood glucose 

levels stay in the normal range. But when 

insulin production falters because of beta cell 

dysfunction, glucose levels rise, leading to 

prediabetes or diabetes. 
6 Causes of Diabetes

Abnormal Glucose Production 

by the Liver

In some people with diabetes, an abnormal 

increase in glucose production by the liver 

also contributes to high blood glucose levels. 

Normally, the pancreas releases the hormone 

glucagon when blood glucose and insulin 

levels are low. Glucagon stimulates the liver 

to produce glucose and release it into the 

bloodstream. But when blood glucose and 

insulin levels are high after a meal, glucagon 

levels drop, and the liver stores excess 

glucose for later, when it is needed. For 

reasons not completely understood, in many 

people with diabetes, glucagon levels stay 

higher than needed. High glucagon levels 

cause the liver to produce unneeded glucose, 

which contributes to high blood glucose 

levels. Metformin, the most commonly used 

drug to treat type 2 diabetes, reduces glucose 

production by the liver.

The Roles of Insulin and Glucagon in Normal Blood Glucose 

Regulation

A healthy person’s body keeps blood glucose levels in a normal range through several 

complex mechanisms. Insulin and glucagon, two hormones made in the pancreas, help 

regulate blood glucose levels:

•	 Insulin, made by beta cells, lowers elevated blood glucose levels.

•	 Glucagon, made by alpha cells, raises low blood glucose levels.

When blood glucose levels rise after a meal, 

the pancreas releases insulin into the blood.

•	 Insulin helps muscle, fat, and liver cells 

absorb glucose from the bloodstream, 

lowering blood glucose levels. 

•	 Insulin stimulates the liver and muscle 

tissue to store excess glucose. The stored 

form of glucose is called glycogen. 

•	 Insulin also lowers blood glucose levels by 

reducing glucose production in the liver.

When blood glucose levels drop overnight or 

due to a skipped meal or heavy exercise, the 

pancreas releases glucagon into the blood.

•	 Glucagon signals the liver and muscle 

tissue to break down glycogen into 

glucose, which enters the bloodstream and 

raises blood glucose levels.

•	 If the body needs more glucose, glucagon 

stimulates the liver to make glucose from 

amino acids. 

Insulin and glucagon help regulate blood glucose 

levels.

Low blood 

glucose

Pancreas

High blood 

glucose

Glucagon 

released by 

pancreas

Insulin 

released by 

pancreas

Liver 

releases 

glucose 

into blood

Normal blood glucose levels

Body’s cells 

absorb 

glucose 

from blood
7 Causes of Diabetes

Metabolic Syndrome

Metabolic syndrome, also called insulin 

resistance syndrome, refers to a group of 

conditions common in people with insulin 

resistance, including

•	 higher than normal blood glucose levels

•	 increased waist size due to excess 

abdominal fat

•	 high blood pressure

•	 abnormal levels of cholesterol and 

triglycerides in the blood

People with metabolic syndrome have an 

increased risk of developing type 2 diabetes 

and CVD. Many studies have found that 

lifestyle changes, such as being physically 

active and losing excess weight, are the best 

ways to reverse metabolic syndrome, improve 

the body’s response to insulin, and reduce 

risk for type 2 diabetes and CVD.

Cell Signaling and Regulation

Cells communicate through a complex 

network of molecular signaling pathways. 

For example, on cell surfaces, insulin 

receptor molecules capture, or bind, insulin 

molecules circulating in the bloodstream. 

This interaction between insulin and its 

receptor prompts the biochemical signals 

that enable the cells to absorb glucose from 

the blood and use it for energy.

Problems in cell signaling systems can 

set off a chain reaction that leads to 

diabetes or other diseases. Many studies 

have focused on how insulin signals cells 

to communicate and regulate action. 

Researchers have identified proteins and 

pathways that transmit the insulin signal and 

have mapped interactions between insulin 

and body tissues, including the way insulin 

helps the liver control blood glucose levels. 

Researchers have also found that key signals 

also come from fat cells, which produce 

substances that cause inflammation and 

insulin resistance. 

This work holds the key to combating 

insulin resistance and diabetes. As 

scientists learn more about cell signaling 

systems involved in glucose regulation, they 

will have more opportunities to develop 

effective treatments.
8 Causes of Diabetes

Beta Cell Dysfunction

Scientists think beta cell dysfunction is a 

key contributor to type 2 diabetes. Beta 

cell impairment can cause inadequate or 

abnormal patterns of insulin release. Also, 

beta cells may be damaged by high blood 

glucose itself, a condition called glucose 

toxicity.

Scientists have not determined the causes 

of beta cell dysfunction in most cases. 

Single gene defects lead to specific forms 

of diabetes called maturity-onset diabetes 

of the young (MODY). The genes involved 

regulate insulin production in the beta 

cells. Although these forms of diabetes are 

rare, they provide clues as to how beta cell 

function may be affected by key regulatory 

factors. Other gene variants are involved 

in determining the number and function of 

beta cells. But these variants account for 

only a small percentage of type 2 diabetes 

cases. Malnutrition early in life is also 

being investigated as a cause of beta cell 

dysfunction. The metabolic environment 

of the developing fetus may also create a 

predisposition for diabetes later in life.

Risk Factors for Type 2 

Diabetes

People who develop type 2 diabetes 

are more likely to have the following 

characteristics:

•	 age 45 or older

•	 overweight or obese

•	 physically inactive

•	 parent or sibling with diabetes

•	 family background that is African 

American, Alaska Native, American 

Indian, Asian American, Hispanic/

Latino, or Pacific Islander American

•	 history of giving birth to a baby 

weighing more than 9 pounds 

•	 history of gestational diabetes

•	 high blood pressure—140/90 or 

above—or being treated for high 

blood pressure

•	 high-density lipoprotein (HDL), or 

good, cholesterol below 35 milligrams 

per deciliter (mg/dL), or a triglyceride 

level above 250 mg/dL

•	 polycystic ovary syndrome, also called 

PCOS 

•	 prediabetes—an A1C level of 5.7 to 

6.4 percent; a fasting plasma glucose 

test result of 100–125 mg/dL, called 

impaired fasting glucose; or a 2-hour 

oral glucose tolerance test result of 

140–199, called impaired glucose 

tolerance

•	 acanthosis nigricans, a condition 

associated with insulin resistance, 

characterized by a dark, velvety rash 

around the neck or armpits 

•	 history of CVD

The American Diabetes Association 

(ADA) recommends that testing to 

detect prediabetes and type 2 diabetes be 

considered in adults who are overweight or 

obese and have one or more additional risk 

factors for diabetes. In adults without these 

risk factors, testing should begin at age 45. 
9 Causes of Diabetes

What causes gestational 

diabetes?

Scientists believe gestational diabetes 

is caused by the hormonal changes and 

metabolic demands of pregnancy together 

with genetic and environmental factors. 

Insulin Resistance and Beta Cell 

Dysfunction

Hormones produced by the placenta and 

other pregnancy-related factors contribute to 

insulin resistance, which occurs in all women 

during late pregnancy. Insulin resistance 

increases the amount of insulin needed to 

control blood glucose levels. If the pancreas 

can’t produce enough insulin due to beta cell 

dysfunction, gestational diabetes occurs.

As with type 2 diabetes, excess weight is 

linked to gestational diabetes. Overweight 

or obese women are at particularly high risk 

for gestational diabetes because they start 

pregnancy with a higher need for insulin due 

to insulin resistance. Excessive weight gain 

during pregnancy may also increase risk.

Family History

Having a family history of diabetes is 

also a risk factor for gestational diabetes, 

suggesting that genes play a role in its 

development. Genetics may also explain 

why the disorder occurs more frequently 

in African Americans, American Indians, 

and Hispanics/Latinos. Many gene variants 

or combinations of variants may increase 

a woman’s risk for developing gestational 

diabetes. Studies have found several gene 

variants associated with gestational diabetes, 

but these variants account for only a small 

fraction of women with gestational diabetes.

Future Risk of Type 2 Diabetes

Because a woman’s hormones usually return 

to normal levels soon after giving birth, 

gestational diabetes disappears in most 

women after delivery. However, women who 

have gestational diabetes are more likely 

to develop gestational diabetes with future 

pregnancies and develop type 2 diabetes.3 

Women with gestational diabetes should be 

tested for persistent diabetes 6 to 12 weeks 

after delivery and at least every 3 years 

thereafter.

3National diabetes statistics report, 2014. Centers for 

Disease Control and Prevention website. www.cdc.gov/

diabeteS/pubs/statsreport14 htm. Updated June 13, 2014. 

Accessed June 16, 2014.

Also, exposure to high glucose levels 

during gestation increases a child’s risk 

for becoming overweight or obese and for 

developing type 2 diabetes later on. The 

result may be a cycle of diabetes affecting 

multiple generations in a family. For both 

mother and child, maintaining a healthy body 

weight and being physically active may help 

prevent type 2 diabetes. 
10 Causes of Diabetes

Other Types and Causes 

of Diabetes

Other types of diabetes have a variety of 

possible causes.

Genetic Mutations Affecting 

Beta Cells, Insulin, and Insulin 

Action

Some relatively uncommon forms of 

diabetes known as monogenic diabetes 

are caused by mutations, or changes, in a 

single gene. These mutations are usually 

inherited, but sometimes the gene mutation 

occurs spontaneously. Most of these gene 

mutations cause diabetes by reducing beta 

cells’ ability to produce insulin.

The most common types of monogenic 

diabetes are neonatal diabetes mellitus 

(NDM) and MODY. NDM occurs in the 

first 6 months of life. MODY is usually 

found during adolescence or early adulthood 

but sometimes is not diagnosed until later 

in life. For more information about NDM 

and MODY, see the NDIC fact sheet 

Monogenic Forms of Diabetes at www.diabetes.

niddk.nih.gov.

Other rare genetic mutations can cause 

diabetes by damaging the quality of 

insulin the body produces or by causing 

abnormalities in insulin receptors.

Other Genetic Diseases

Diabetes occurs in people with Down 

syndrome, Klinefelter syndrome, and 

Turner syndrome at higher rates than 

the general population. Scientists are 

investigating whether genes that may 

predispose people to genetic syndromes 

also predispose them to diabetes. 

The genetic disorders cystic fibrosis and 

hemochromatosis are linked to diabetes. 

Cystic fibrosis produces abnormally thick 

mucus, which blocks the pancreas. The risk 

of diabetes increases with age in people 

with cystic fibrosis. Hemochromatosis 

causes the body to store too much iron. If 

the disorder is not treated, iron can build 

up in and damage the pancreas and other 

organs.

Damage to or Removal of the 

Pancreas

Pancreatitis, cancer, and trauma can all 

harm the pancreatic beta cells or impair 

insulin production, thus causing diabetes. If 

the damaged pancreas is removed, diabetes 

will occur due to the loss of the beta cells. 
11 Causes of Diabetes

Endocrine Diseases

Endocrine diseases affect organs that 

produce hormones. Cushing’s syndrome 

and acromegaly are examples of hormonal 

disorders that can cause prediabetes and 

diabetes by inducing insulin resistance. 

Cushing’s syndrome is marked by excessive 

production of cortisol—sometimes called 

the “stress hormone.” Acromegaly occurs 

when the body produces too much growth 

hormone. Glucagonoma, a rare tumor of 

the pancreas, can also cause diabetes. The 

tumor causes the body to produce too much 

glucagon. Hyperthyroidism, a disorder that 

occurs when the thyroid gland produces 

too much thyroid hormone, can also cause 

elevated blood glucose levels.

Autoimmune Disorders

Rare disorders characterized by antibodies 

that disrupt insulin action can lead to 

diabetes. This kind of diabetes is often 

associated with other autoimmune disorders 

such as lupus erythematosus. Another 

rare autoimmune disorder called stiff-man 

syndrome is associated with antibodies 

that attack the beta cells, similar to type 1 

diabetes.

Medications and Chemical 

Toxins

Some medications, such as nicotinic acid 

and certain types of diuretics, anti-seizure 

drugs, psychiatric drugs, and drugs to treat 

human immunodeficiency virus (HIV), can 

impair beta cells or disrupt insulin action. 

Pentamidine, a drug prescribed to treat a 

type of pneumonia, can increase the risk of 

pancreatitis, beta cell damage, and diabetes. 

Also, glucocorticoids—steroid hormones 

that are chemically similar to naturally 

produced cortisol—may impair insulin 

action. Glucocorticoids are used to treat 

inflammatory illnesses such as rheumatoid 

arthritis, asthma, lupus, and ulcerative colitis.

Many chemical toxins can damage or 

destroy beta cells in animals, but only a few 

have been linked to diabetes in humans. 

For example, dioxin—a contaminant of 

the herbicide Agent Orange, used during 

the Vietnam War—may be linked to the 

development of type 2 diabetes. In 2000, 

based on a report from the Institute of 

Medicine, the U.S. Department of Veterans 

Affairs (VA) added diabetes to the list of 

conditions for which Vietnam veterans are 

eligible for disability compensation. Also, 

a chemical in a rat poison no longer in 

use has been shown to cause diabetes if 

ingested. Some studies suggest a high intake 

of nitrogen-containing chemicals such as 

nitrates and nitrites might increase the risk of 

diabetes. Arsenic has also been studied for 

possible links to diabetes. 

Lipodystrophy

Lipodystrophy is a condition in which fat 

tissue is lost or redistributed in the body. 

The condition is associated with insulin 

resistance and type 2 diabetes. 
12 Causes of Diabetes

Points to Remember

•	 Diabetes is a complex group of diseases 

with a variety of causes. Scientists 

believe genes and environmental factors 

interact to cause diabetes in most cases. 

•	 People with diabetes have high blood 

glucose, also called high blood sugar or 

hyperglycemia. Diabetes develops when 

the body doesn’t make enough insulin 

or is not able to use insulin effectively, 

or both.

•	 Insulin is a hormone made by beta cells 

in the pancreas. Insulin helps cells 

throughout the body absorb and use 

glucose for energy. If the body does not 

produce enough insulin or cannot use 

insulin effectively, glucose builds up in 

the blood instead of being absorbed by 

cells in the body, and the body is starved 

of energy. 

•	 Prediabetes is a condition in which 

blood glucose levels or A1C levels are 

higher than normal but not high enough 

to be diagnosed as diabetes. People 

with prediabetes can substantially 

reduce their risk of developing diabetes 

by losing weight and increasing physical 

activity.

•	 The two main types of diabetes are 

type 1 diabetes and type 2 diabetes. 

Gestational diabetes is a third form 

of diabetes that develops only during 

pregnancy.

•	 Type 1 diabetes is caused by a lack 

of insulin due to the destruction of 

insulin-producing beta cells. In type 1 

diabetes—an autoimmune disease—

the body’s immune system attacks and 

destroys the beta cells. 

•	 Type 2 diabetes—the most common 

form of diabetes—is caused by a 

combination of factors, including insulin 

resistance, a condition in which the 

body’s muscle, fat, and liver cells do not 

use insulin effectively. Type 2 diabetes 

develops when the body can no longer 

produce enough insulin to compensate 

for the impaired ability to use insulin.

•	 Scientists believe gestational 

diabetes is caused by the hormonal 

changes and metabolic demands of 

pregnancy together with genetic and 

environmental factors. Risk factors 

for gestational diabetes include being 

overweight and having a family history 

of diabetes. 

•	 Monogenic forms of diabetes are 

relatively uncommon and are caused 

by mutations in single genes that limit 

insulin production, quality, or action in 

the body. 

•	 Other types of diabetes are caused 

by diseases and injuries that damage 

the pancreas; certain chemical toxins 

and medications; infections; and other 

conditions.
13 Causes of Diabetes

Hope through Research

The National Institute of Diabetes and 

Digestive and Kidney Diseases (NIDDK) 

conducts and supports research into many 

kinds of disorders, including diabetes. 

Researchers throughout the United 

States and the world are working to better 

understand, prevent, and treat this disease. 

Finding ways to prevent or delay diabetes in 

people at risk is a key goal of this research. 

Scientists are identifying genes that may 

be involved in type 1 or type 2 diabetes 

and studying how they work. Studies are 

clarifying the complicated mechanisms that 

damage beta cells in diabetes. A great deal 

of work is also focused on preventing the 

different types of diabetes and improving 

treatment.

The NIDDK conducts research in its own 

laboratories and supports a great deal of 

basic and clinical research in medical centers 

and hospitals throughout the United States. 

Several other components of the NIH also 

conduct and support research related to 

diabetes. Other Government agencies that 

sponsor diabetes programs are the Centers 

for Disease Control and Prevention, 

the Indian Health Service, the Health 

Resources and Services Administration, the 

VA, and the U.S. Department of Defense. 

In addition, many organizations outside the 

Government support diabetes research and 

education activities. These organizations 

include the ADA, the Juvenile Diabetes 

Research Foundation International, 

the American Association of Diabetes 

Educators, the American Association 

of Clinical Endocrinologists, and The 

Endocrine Society. 

Clinical trials are research studies involving 

people. Clinical trials look at safe and 

effective new ways to prevent, detect, or 

treat disease. Researchers also use clinical 

trials to look at other aspects of care, such 

as improving the quality of life for people 

with chronic illnesses. To learn more about 

clinical trials, why they matter, and how to 

participate, visit the NIH Clinical Research 

Trials and You website at www.nih.gov/

health/clinicaltrials. For information about 

current studies, visit www.ClinicalTrials.gov.
14 Causes of Diabetes

For More Information

American Association of Diabetes Educators

200 West Madison Street, Suite 800

Chicago, IL 60606

Phone: 1–800–338–3633

Internet: www.diabeteseducator.org

American Diabetes Association

1701 North Beauregard Street

Alexandria, VA 22311

Phone: 1–800–DIABETES 

 (1–800–342–2383)

Email: askADA@diabetes.org

Internet: www.diabetes.org

Immune Tolerance Network

Office of the Director

Administrative Operations

Benaroya Research Institute

1201 Ninth Avenue

Seattle, WA 98101–2795

Phone: 206–342–6562

Fax: 206–342–6588

Email: director@immunetolerance.org

Internet: www.immunetolerance.org

JDRF

26 Broadway, 14th Floor

New York, NY 10004

Phone: 1–800–533–CURE (1–800–533–2873)

Fax: 212–785–9595

Email: info@jdrf.org

Internet: www.jdrf.org

Acknowledgments

Publications produced by the Clearinghouse 

are carefully reviewed by both NIDDK 

scientists and outside experts. This 

publication was reviewed by Alan Shuldiner, 

M.D., University of Maryland.

You may also find additional information about this 

topic by visiting MedlinePlus at www.medlineplus.gov.

This publication may contain information about 

medications and, when taken as prescribed, 

the conditions they treat. When prepared, this 

publication included the most current information 

available. For updates or for questions about 

any medications, contact the U.S. Food and Drug 

Administration toll-free at 1–888–INFO–FDA 

(1–888–463–6332) or visit www.fda.gov. Consult your 

health care provider for more information.
15 Causes of Diabetes

National Diabetes Education 

Program

1 Diabetes Way

Bethesda, MD 20814–9692

Phone: 1–888–693–NDEP 

 (1–888–693–6337)

TTY: 1–866–569–1162

Fax: 703–738–4929

Email: ndep@mail.nih.gov

Internet: www.ndep.nih.gov

 www.yourdiabetesinfo.org

The National Diabetes Education Program 

is a federally funded program sponsored by 

the U.S. Department of Health and Human 

Services’ National Institutes of Health 

and the Centers for Disease Control and 

Prevention and includes over 200 partners at 

the federal, state, and local levels, working 

together to reduce the morbidity and 

mortality associated with diabetes.
National Diabetes 

Information Clearinghouse

1 Information Way 

Bethesda, MD 20892–3560 

Phone: 1–800–860–8747

TTY: 1–866–569–1162

Fax: 703–738–4929

Email: ndic@info.niddk.nih.gov 

Internet: www.diabetes.niddk.nih.gov

The National Diabetes Information 

Clearinghouse (NDIC) is a service of the 

National Institute of Diabetes and Digestive 

and Kidney Diseases (NIDDK). The 

NIDDK is part of the National Institutes of 

Health of the U.S. Department of Health 

and Human Services. Established in 1978, 

the Clearinghouse provides information 

about diabetes to people with diabetes and 

their families, health care professionals, and 

the public. The NDIC answers inquiries, 

develops and distributes publications, and 

works closely with professional and patient 

organizations and Government agencies to 

coordinate resources about diabetes.

This publication is not copyrighted. The 

Clearinghouse encourages users of this publication to 

duplicate and distribute as many copies as desired.

This publication is available at 

www.diabetes.niddk.nih.gov.

NIH Publication No. 14–5164

June 2014

The NIDDK prints on recycled paper with bio-based ink.