Type 1 diabetes

What is Type 1 diabetes?

Type 1 diabetes is a lifelong (chronic) disease in which there is a high level of sugar (glucose) in the blood.


Type 1 diabetes can occur at any age. It is most often diagnosed in children, adolescents, or young adults.

Insulin is a hormone produced in the pancreas by special cells called beta cells. The pancreas is below and behind the stomach. Insulin is needed to move blood sugar (glucose) into cells. Inside the cells, glucose is stored and later used for energy. With type 1 diabetes, beta cells produce little or no insulin.

Without enough insulin, glucose builds up in the bloodstream instead of going into the cells. This buildup of glucose in the blood is called hyperglycemia. The body is unable to use the glucose for energy. This leads to the symptoms of type 1 diabetes.

The exact cause of type 1 diabetes is unknown. Most likely it is an autoimmune disorder. This is a condition that occurs when the immune system mistakenly attacks and destroys healthy body tissue. With type 1 diabetes, an infection or another trigger causes the body to mistakenly attack the cells in the pancreas that make insulin. The tendency to develop autoimmune diseases, including type 1 diabetes, can be passed down through families.



The following symptoms may be the first signs of type 1 diabetes. Or they may occur when blood sugar is high.

  • Being very thirsty
  • Feeling hungry
  • Feeling tired all the time
  • Having blurry eyesight
  • Feeling numbness or tingling in your feet
  • Losing weight without trying
  • Urinating more often (including urinating at night or bedwetting in children who were dry overnight before)

For other people, these serious warning symptoms may be the first signs of type 1 diabetes. Or, they may happen when blood sugar is very high (diabetic ketoacidosis):

  • Deep, rapid breathing
  • Dry skin and mouth
  • Flushed face
  • Fruity breath odor
  • Nausea or vomiting; inability to keep down fluids
  • Stomach pain


Low blood sugar (hypoglycemia) can develop quickly in people with diabetes who are taking insulin. Symptoms usually appear when a person’s blood sugar level falls below 70 milligrams per deciliter (mg/dL). Watch for:

  • Headache
  • Hunger
  • Nervousness
  • Rapid heartbeat (palpitations)
  • Shaking
  • Sweating
  • Weakness

Exams and Tests

Diabetes is diagnosed with the following blood tests:

  • Fasting blood glucose level: Diabetes is diagnosed if it is higher than 126 mg/dL two different  times.
  • Random (non-fasting) blood glucose level. You may have diabetes if it is higher than 200 mg/dL, and you have symptoms such as increased thirst, urination, and fatigue. (This must be confirmed with a fasting test.)
  • Oral glucose tolerance test: Diabetes is diagnosed if the glucose level is higher than 200 mg/dL 2 hours after you drink a special sugar drink.
  • Hemoglobin A1c (A1C) test: Diabetes is diagnosed if the result of the test is 6.5% or higher.

Ketone testing is also used sometimes. The ketone test is done using a urine sample or blood sample. Ketone testing may be done:

  • When the blood sugar is higher than 240 mg/dL
  • During an illness such as pneumonia, heart attack, or stroke
  • When nausea or vomiting occur
  • During pregnancy

The following tests or exams will help you and your doctor monitor your diabetes and prevent problems caused by diabetes:

  • Check the skin and bones on your feet and legs.
  • Check if your feet are getting numb (diabetic nerve disease).
  • Have your blood pressure checked at least once a year. The goal should be 140/80 mm Hg or lower.
  • Have an A1C test done every 6 months if your diabetes is well controlled. Have the test done every 3 months if your diabetes is not well controlled.
  • Have your cholesterol and triglyceride levels checked once a year.
  • Get tests once a year to make sure your kidneys are working well (microalbuminuria and serum creatinine).
  • Visit your eye doctor at least once a year, or more often if you have signs of diabetic eye disease.
  • See the dentist every 6 months for a thorough dental cleaning and exam. Make sure your dentist and hygienist know that you have diabetes.