Type 1 Diabetes - Symptoms and Causes (2023)

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Type 1 diabetes, formerly known as juvenile diabetes or insulin-dependent diabetes, is a chronic disease. In this condition, the pancreas produces little or no insulin. Insulin is a hormone that the body uses to allow sugar (glucose) to enter cells for energy.

Various factors, including genetics and certain viruses, can cause type 1 diabetes. Although type 1 diabetes usually develops in childhood or adolescence, it can also develop in adults.

Even according to many studies, there is no cure for type 1 diabetes. The goal of treatment is to control the amount of sugar in the blood using insulin, diet, and lifestyle to prevent complications.


Type 1 diabetes symptoms can appear suddenly and include:

  • feeling thirstier than usual
  • frequent urination
  • Children who never wet the bed at night
  • feeling hungry
  • lose weight without trying
  • restlessness or other mood swings
  • feeling tired and weak
  • blurry vision

When should you see a doctor?

If you notice any of these symptoms in you or your child, talk to your doctor.

request an appointment

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The exact cause of type 1 diabetes is unknown. Normally, the body's immune system normally fights off harmful bacteria and viruses that destroy the cells in the pancreas that produce insulin (the islets). Other possible causes are:

  • heredity
  • exposure to viruses and other environmental factors

Insulin action

Once large numbers of islet cells are destroyed, the body produces little or no insulin. Insulin is a hormone that comes from the gland behind and below the stomach (pancreas).

  • The pancreas secretes insulin into the blood.
  • Insulin travels through the body and ensures that sugar gets into the cells.
  • Insulin lowers the amount of sugar in your blood.
  • When blood sugar levels drop, the pancreas releases less insulin into the blood.

The role of glucose

Glucose (a type of sugar) is the main source of energy for the cells that make up muscles and other tissues.

  • Glucose has two main sources: food and the liver.
  • The sugar is absorbed into the bloodstream and into the cells with the help of insulin.
  • The liver stores glucose in the form of glycogen.
  • When blood sugar levels are low, such as when you haven't eaten for a long time, the liver breaks down stored glycogen into glucose. This keeps blood sugar levels within typical ranges.

In type 1 diabetes, there is no insulin to move glucose into cells. This causes an increase in sugar in the blood. This can lead to life-threatening complications.

risk factors

Factors that may increase the risk of type 1 diabetes include:

  • family history.Anyone with a parent or sibling with type 1 diabetes has a slightly higher risk of developing the disease.
  • genetic.The presence of certain genes increases the risk of developing type 1 diabetes.
  • geography.The number of people with type 1 diabetes tends to increase with distance from the equator.
  • Change.Type 1 diabetes can occur at any age, but has two distinct peaks. The first peak occurs in children between 4 and 7 years old. The second affects children aged 10 to 14.


Over time, complications of type 1 diabetes can affect vital organs in the body. These organs include the heart, blood vessels, nerves, eyes and kidneys. Normal blood sugar levels reduce the risk of many complications.

Complications of diabetes can be disabling and even life-threatening.

  • Heart and blood vessel disease.Diabetes increases the risk of some heart and blood vessel problems. These conditions include coronary heart disease (angina) with chest pain, heart attack, stroke, narrowing of arteries (atherosclerosis), and high blood pressure.
  • Nerve damage (neuropathy).Too much sugar in the blood can damage the walls of the tiny blood vessels (capillaries) that supply nerves. This is especially true for the legs. This may cause tingling, numbness, burning, or pain. This usually starts on the toes or fingertips and works its way up. Over time, poor blood sugar control can cause you to lose all feeling in the affected limb.

    Damage to the nerves that affect the digestive system may cause problems such as nausea, vomiting, diarrhea, or constipation. For men, erectile dysfunction can be a problem.

  • Kidney damage (nephropathy).The kidneys have millions of tiny blood vessels that keep waste products from entering the blood. Diabetes can damage this system. Severe damage can lead to kidney failure or irreversible end-stage renal disease. End-stage renal disease must be treated with mechanical filtration of the kidneys (dialysis) or a kidney transplant.
  • Eye damage.Diabetes can damage blood vessels in the retina (the part of the eye that sees light) (diabetic retinopathy). This may cause blindness. Diabetes also increases the risk of other serious vision problems, such as cataracts and glaucoma.
  • foot injury.Nerve damage to the feet or poor circulation in the feet can increase the risk of certain foot complications. Cuts and blisters can lead to serious infections if left untreated. These infections may need to be treated by removing the toe, foot, or leg (amputation).
  • Skin and Oral Diseases.Diabetes can make you more susceptible to skin and mouth infections. These include bacterial and fungal infections. Gum disease and dry mouth are also more likely.
  • pregnancy complications.High blood sugar can be dangerous for both parents and babies. When diabetes is poorly controlled, the risk of miscarriage, stillbirth and birth defects increases. For parents, diabetes increases the risk of diabetic ketoacidosis, diabetic eye problems (retinopathy), pregnancy-related high blood pressure, and preeclampsia.


There is currently no known way to prevent type 1 diabetes. However, researchers are working to prevent this disease or further damage to islet cells in the newly diagnosed population.

Ask your doctor if you are eligible to participate in one of these clinical trials. It is important to carefully weigh the risks and benefits of each treatment available in the study.

Mayo Clinic experiences and patient stories

Our patients tell us that the quality of their interactions, our attention to detail and the efficiency of their visits mean they will have an unprecedented healthcare experience. Check out the stories of satisfied patients at Mayo Clinic.

  1. Pancreas Transplant for Diabetes In 2017, 48-year-old Lynn Guzik suffered a sudden and severe heart attack. Lynn has had insulin-dependent diabetes for over 20 years and has struggled to manage her diabetes, but has never had a heart attack before. However, her heart was so damaged that Lynn underwent a heart transplant in 2017 in her then hometown of Houston, Texas. Despite her new heart, Lynn is still barely functioning as a mother of two...  

Mayo Clinic staff

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May 3, 2023

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