Everything You Need to Know About Type 1 Diabetes

Learn what causes this condition, early symptoms to recognize, and how it's treated.

A couple looks at a glucose monitor's results, as they manage type 1 diabetes and learn about onset, symptoms and more.

Updated on March 25, 2024.

For a long time, type 1 diabetes was considered a disease that affects young people. In fact, it used to be called juvenile-onset diabetes because it’s usually diagnosed in children, teenagers, and young adults. Even though symptoms usually show up in young people, type 1 diabetes can also affect adults.

Unlike type 2 diabetes, lifestyle choices such as diet and exercise won’t affect your risk of developing type 1 diabetes. Its exact causes are a mystery, but it’s thought that type 1 diabetes is caused by genetics and an autoimmune response, or when the body's immune system attacks healthy cells. These things along with something in a person's environment, such as a virus, may provide a trigger that causes the condition to develop. Type 1 diabetes is much less common than type 2. Only about 5 to 10 percent of all cases of diabetes are type 1. 

Understanding blood sugar and insulin 

While type 2 diabetes is caused by problems with the way the body processes insulin, type 1 diabetes develops when the body does not produce enough insulin. Insulin is a hormone produced in the pancreas. It helps draw glucose (sugar) from the blood and into the body’s cells for use as fuel. In those with type 1 diabetes, the immune system attacks the cells in the pancreas that produce insulin so the body either produces no insulin or not enough. 

When your cells can’t draw glucose out of the bloodstream, it builds up, leading to a condition called hyperglycemia (or high blood sugar).  

Type 1 diabetes symptoms 

Type 1 diabetes onset can be gradual or sudden and severe, with symptoms including extreme thirst, fatigue, frequent urination, weight loss, and blurred vision. 

People with type 1 diabetes can develop diabetic ketoacidosis (DKA), as well. DKA occurs when the body doesn't have enough insulin to allow blood sugar into cells where it can be used as energy. For some people who have not yet been diagnosed, DKA can be the first sign of type 1 diabetes. When your cells can’t burn glucose for energy, they burn fat. This process releases molecules called ketones, which make the blood acidic. DKA often develops gradually with vague symptoms like feeling extra thirsty or urinating more than usual. Additional symptoms of DKA can include nausea and vomiting, abdominal pain, difficulty breathing, breath that smells sugary or fruity, and confusion.  

Diabetic ketoacidosis is an emergency. Call 911 or go to the emergency room if you notice any of these symptoms and suspect DKA. 

How to know if you have type 1 diabetes 

Diabetes is diagnosed by one of four blood tests that measure the amount of sugar in the bloodstream:

  • The A1C test measures the average level of blood sugar over the previous three months. 
  • The fasting plasma glucose test measures blood sugar after an overnight fast. 
  • The oral glucose tolerance test measures blood sugar levels after fasting and one hour or two hours after drinking a glucose-rich beverage. 
  • The random plasma glucose test measures your blood sugar at any time the test is given, even if you have not fasted beforehand.

Once a person is diagnosed with diabetes, the next question is whether it is type 1 or type 2. Sometimes this is obvious, as in the case of a young child who is not overweight and is physically very active. But when diabetes is diagnosed in an adult, it is not always certain which type the person has. Someone who is overweight or obese or who has a strong family history of diabetes is most likely to have type 2 diabetes. But someone who is a bit younger—especially in their 30s or 40s—or who is fit or has no family history of diabetes may have type 1 diabetes. Blood tests may help make the proper diagnosis, but sometimes the situation only becomes clear with the passage of time. 

Monitoring blood sugar if you have type 1 diabetes 

Once you know you have type 1 diabetes, it’s important to monitor your blood sugar. You’ll be checking your blood sugar levels several times a day, either by pricking your fingertips and getting a reading with a blood glucose meter or by using a continuous glucose monitor. Your healthcare provider (HCP) will also test your A1C levels once every three months to keep tabs on long-term control. 

Target levels, according to the American Diabetes Association (ADA), are as follows.

  • A1C: below 7 percent 
  • Pre-meal blood sugar (also known as preprandial plasma glucose): between 80 and 130 milligrams per deciliter (mg/dl) 
  • Post-meal blood sugar, taken 1 to 2 hours after the beginning of a meal (also known as postprandial plasma glucose): less than 180 mg/dl 

Because targets may vary based on factors such as age, check with your HCP about what levels are right for you. 


One of the biggest differences between type 1 and type 2 diabetes is that everyone with type 1 diabetes needs insulin. 

Intensive insulin therapy—taking three or more shots per day or using an insulin pump, as well as checking your blood sugar four or more times a day—is fairly typical if you have type 1 diabetes.  

Taking too much insulin at once, not eating enough, exercising without eating, waiting too long between meals, or drinking too much alcohol can increase your risk of having too little glucose in the bloodstream—a condition known as hypoglycemia. 

Symptoms of hypoglycemia include anxiety, sweating, shaking, hunger, difficulty walking, weakness, confusion, and bizarre behavior or personality changes. Check with your HCP about what steps to take in advance should you develop hypoglycemia, such as having an emergency stash of sugar to help in these situations. 

Managing your type 1 diabetes 

Getting enough exercise and maintaining a healthy diet are crucial to any diabetes treatment regimen. Exercise helps clear glucose from the bloodstream and will help you maintain a healthy weight. The Centers for Disease Control and Prevention recommends at least 150 minutes per week of moderate-intensity aerobic exercise, like taking brisk walks or pushing a lawn mower, along with two or more days of muscle-strengthening activities like doing sit-ups or heavy gardening such as digging or shoveling.  

It’s important to be mindful of your body’s blood glucose response to exercise, so be sure to check with your HCP before beginning or altering your workout program. 

Choosing healthy foods is also important. For those with diabetes, their diet should be low in sodium, cholesterol, and fat—but high in fiber, which is found in fruits, vegetables, and whole grains. The ADA notes that a variety of eating patterns may be helpful in managing diabetes and preventing related complications like high blood pressure and heart disease. These include the DASH diet, Mediterranean-style diet, a low-carb diet, a low-fat diet, or a vegan or vegetarian diet.

Article sources open article sources

Centers for Disease Control and Prevention. What is Type 1 Diabetes? Last reviewed March 11, 2022.
Centers for Disease Control and Prevention. Diabetic ketoacidosis. Last reviewed March 25, 2021.
Centers for Disease Control and Prevention. Physical Activity Adults. Last reviewed June 2, 2022.
American Diabetes Association Professional Practice Committee. 10. Cardiovascular Disease and Risk Management: Standards of Medical Care in Diabetes-2022. Diabetes Care. 2022 Jan 1;45(Suppl 1):S144-S174.

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