context: Type 1 diabetes happens when your immune system destroys cells in your pancreas called beta cells. They're the ones that make insulin. Some people get a condition called secondary diabetes. It's similar to type 1, except the immune system doesn't destroy your beta cells. They're wiped out by something else, like a disease or an injury to your pancreas. Insulin is a hormone that helps move sugar, or glucose, into your body's tissues. Cells use it as fuel. Damage to beta cells from type 1 diabetes throws the process off. Glucose doesn't move into your cells because insulin isn't there to do it. Instead it builds up in your blood and your cells starve. This causes high blood sugar, which can lead to: Dehydration. When there's extra sugar in your blood, you pee more. That's your body's way of getting rid of it. A large amount of water goes out with that urine, causing your body to dry out. Weight loss. The glucose that goes out when you pee takes calories with it. That's why many people with high blood sugar lose weight. Dehydration also plays a part. Diabetic ketoacidosis ( DKA). If your body can't get enough glucose for fuel, it breaks down fat cells instead. This creates chemicals called ketones. Your liver releases the sugar it stores to help out. But your body can't use it without insulin, so it builds up in your blood, along with the acidic ketones. This combination of extra glucose, dehydration, and acid buildup is known as "ketoacidosis" and can be life-threatening if not treated right away. Damage to your body. Over time, high glucose levels in your blood can harm the nerves and small blood vessels in your eyes, kidneys, and heart. They can also make you more likely to get hardening of the arteries, or atherosclerosis, which can lead to heart attacks and strokes. It's rare. Only about 5% of people with diabetes have type 1. It's more common in whites than in African- Americans. It affects men and women equally. Although the disease usually starts in people under 20, it can happen at any age. Doctors don't know all the things that lead to type 1 diabetes. But they do know your genes play a role. They also know type 1 diabetes can result when something in the environment, like a virus, tells your immune system to go after your pancreas. Most people with type 1 diabetes have signs of this attack, called autoantibodies. They're present in almost everyone who has the condition when their blood sugar is high. Type 1 diabetes can happen along with other autoimmune diseases, like Grave's disease or vitiligo. These are often subtle, but they can become severe. They include: Heavy thirst Increased hunger (especially after eating) Dry mouth Nausea and vomiting Pain in your belly Frequent urination Unexplained weight loss (even though you're eating and feel hungry) Fatigue (weak, tired feeling) Blurred vision Heavy, labored breathing (your doctor will call this Kussmaul respiration) Frequent infections of the skin, urinary tract, or vagina Signs of an emergency with type 1 diabetes include: Shaking and confusion Rapid breathing Fruity smell to your breath Pain in your belly Loss of consciousness (rare) If your doctor thinks you have type 1 diabetes, he'll check your blood sugar levels. He may test your urine for glucose or chemicals your body makes when you don't have enough insulin. Right now there's no way to prevent type 1 diabetes. Many people with type 1 diabetes live long, healthy lives. The key to good health is to keep your blood sugar levels within the range your doctor gives you. You'll need to check them often and adjust insulin, food, and activities to make that happen. All people with type 1 diabetes must use insulin injections to control their blood sugar. When your doctor talks about insulin, he'll mention three main things: " Onset" is the length of time before it reaches your bloodstream and begins lowering blood sugar. " Peak time" is the time when insulin is doing the most work in terms of lowering blood sugar. " Duration" is how long it keeps working after onset. Several types of insulin are available. Rapid-acting starts to work in about 15 minutes. It peaks around 1 hour after you take it and continues to work for 2 to 4 hours. Regular or short-acting gets to work in about 30 minutes. It peaks between 2 and 3 hours and keeps working for 3 to 6 hours. Intermediate-acting won't get into your bloodstream for 2 to 4 hours after injection. It peaks from 4 to 12 hours and works for 12 to 18 hours. Long-acting takes several hours to get into your system and lasts for about 24 hours. Your doctor may start you out with two injections a day of two different types of insulin. You may progress to three or four shots a day. Most insulin comes in a small glass bottle called a vial. You draw it out with a syringe that has a needle on the end, and give yourself the shot. Some now comes in a prefilled pen. One kind is inhaled. You can also get it from a pump -- a device you wear that sends it into your body via a small tube. Your doctor will help you to pick the type and the delivery method that's best for you. Exercise is an important part of treating type 1. But it isn't as simple as going out for a run. You have to balance your insulin dose and the food you eat with any activity, even simple tasks around the house or yard. Knowledge is power. Check your blood sugar before, during, and after an activity to find out how it affects you. Some things will make your levels go up; others won't. You can lower your insulin or have a snack with carbs to prevent it from dropping too low. If your test is high, test for ketones -- acids that can result from high sugar levels. If they're OK, you should be good to go. If they're high, skip the workout. You'll also need to understand how food affects your blood sugar. Once you know the roles that carbs, fats, and protein play, you can build a healthy eating plan that helps keep your levels where they should be. A diabetes educator or registered dietitian can help you get started. If you don't keep your type 1 diabetes well controlled, you could set yourself up for serious or life-threatening problems: Retinopathy. This eye problem happens in about 80% of adults who have had type 1 diabetes for more than 15 years. It's rare before puberty no matter how long you've had the disease. To prevent it -- and keep your eyesight -- keep good control of blood sugar, blood pressure, cholesterol, and triglycerides. Kidney damage. About 20% to 30% of people with type 1 diabetes get a condition called nephropathy. The chances grow over time. It's most likely to show up 15 to 25 years after the onset of diabetes. It can lead to other serious problems like kidney failure and heart disease. Poor blood circulation and nerve damage. Damaged nerves and hardened arteries lead to a loss of sensation in and a lack of blood supply to your feet. This raises your chances of injury and makes it harder for open sores and wounds to heal. And when that happens, you could lose a limb. Nerve damage can also cause digestive problems like nausea, vomiting, and diarrhea.