context: Ketosis is a normal process that happens when your body doesn't have enough carbs to burn for energy. Instead, it burns fat and makes substances called ketones, which it can use for fuel. Ketosis is a word you'll probably see when you're looking for information on diabetes or weight loss. Is it a good thing or a bad thing? That depends. Ketosis is a popular weight loss strategy. Low-carb eating plans include the first part of the Atkins diet and the Paleo diet, which stress proteins for fueling your body. In addition to helping you burn fat, ketosis can make you feel less hungry. It also helps you maintain muscle. For healthy people who don't have diabetes and aren't pregnant, ketosis usually kicks in after 3 or 4 days of eating less than 50 grams of carbohydrates per day. That's about 3 slices of bread, a cup of low-fat fruit yogurt, or two small bananas. You can start ketosis by fasting, too. Doctors may put children who have epilepsy on a ketogenic diet, a special high-fat, very low-carb and protein plan because it might help prevent seizures. Adults with epilepsy sometimes eat modified Atkins diets. Some research suggests that ketogenic diets might help lower your risk of heart disease. Other studies show specific very-low-carb diets help people with metabolic syndrome, insulin resistance, and type 2 diabetes. Researchers are also studying the effects of these diets on acne, cancer, polycystic ovary syndrome ( PCOS), and nervous system diseases like Alzheimer's, Parkinson's, and Lou Gehrig's disease. If you're healthy and eating a balanced diet, your body controls how much fat it burns so you don't normally make or use ketones. But when you cut way back on your calories or carbs, your body will switch to ketosis for energy. It can also happen after you exercise for a long time and during pregnancy. During the first week of following a keto diet, you might start to feel bad. Some doctors think this is due to sugar and carbohydrate withdrawal. Or it could be changes to your gut bacteria or even an immune system reaction. You might notice temporary side effects such as: Headache Fatigue Brain fog Irritability Constipation Trouble sleeping Nausea Stomachache Dizziness Sugar cravings Cramps Sore muscles Bad breath Some people call this the "keto flu," though this isn't an official medical condition. Drinking plenty of water can ease or help you avoid these symptoms. If you have uncontrolled diabetes, ketosis can become dangerous when ketones build up. High levels lead to dehydration and change the chemical balance of your blood. It becomes acidic and can cause a coma or death. People with diabetes can get ketoacidosis, or diabetic ketoacidosis ( DKA), when they don't take enough insulin. They can also get DKA when they're sick or injured or they don't get enough fluids and become dehydrated. Some people without diabetes can get ketoacidosis, too. It's caused by alcoholism, starvation, or an overactive thyroid. A healthy low-carb diet shouldn't cause a problem. If you have these symptoms, call your doctor: Thirstiness or a dry mouth Peeing a lot Feeling tired Dry or flushed skin Feeling sick to your stomach Throwing up Trouble breathing Confusion Fruity-smelling breath Pain in your belly When you have diabetes, throwing up can be especially dangerous. Although DKA usually starts off slowly, throwing up can speed up the process so that it happens in just a few hours. Call your doctor if you've been throwing up for 2 hours. You can find out how much ketosis is going on in your body by testing for ketones in your blood or urine. You don't need to go to the doctor. You can buy test strips to check your pee at home. Some blood sugar meters can measure ketones in your blood. If you don't know how and when to test your ketones, talk to your doctor or diabetes instructor. High levels of ketones are dangerous.