What is it?
Type 1 diabetes, once known as juvenile diabetes or insulin-dependent diabetes, is a chronic condition in which the pancreas produces little or no insulin, a hormone needed to allow sugar (glucose) to enter cells to produce energy. Type 2 diabetes, which is far more common, occurs when the body becomes resistant to the effects of insulin or doesn't make enough insulin.
Various factors may contribute to type 1 diabetes, including genetics and exposure to certain viruses. Although type 1 diabetes typically appears during adolescence, it can develop at any age.
Despite active research, type 1 diabetes has no cure, though it can be managed. With proper treatment, people who have type 1 diabetes can expect to live longer, more healthy lives than in the past.
Type 1 diabetes signs and symptoms can come on quickly and may include:
- Increased thirst and frequent urination. As excess sugar builds up in your bloodstream, fluid is pulled from your tissues. This may leave you thirsty. As a result, you may drink — and urinate — more than usual.
- Extreme hunger. Without enough insulin to move sugar into your cells, your muscles and organs become depleted of energy. This triggers intense hunger that may persist even after you eat. Without insulin, the sugar in your food never reaches your energy-starved tissues.
- Weight loss. Despite eating more than usual to relieve hunger, you may lose weight — sometimes rapidly. Without the energy sugar supplies, your muscle tissues and fat stores may simply shrink.
- Fatigue. If your cells are deprived of sugar, you may become tired and irritable.
- Blurred vision. If your blood sugar level is too high, fluid may be pulled from your tissues — including the lenses of your eyes. This may affect your ability to focus clearly.
The exact cause of type 1 diabetes is unknown. Scientists do know that in most people with type 1 diabetes, their body's own immune system — which normally fights harmful bacteria and viruses — mistakenly destroys the insulin-producing (islet) cells in the pancreas. Genetics may play a role in this process, and exposure to certain viruses may trigger the disease.
Whatever the cause, once the islet cells are destroyed, you'll produce little or no insulin. Normally, the hormone insulin helps glucose enter your cells to provide energy to your muscles and tissues. Insulin comes from the pancreas, a gland located just behind the stomach. When everything is working properly, once you eat, the pancreas secretes insulin into the bloodstream. As insulin circulates, it acts like a key by unlocking microscopic doors that allow sugar to enter the body's cells. Insulin lowers the amount of sugar in the bloodstream, and as the blood sugar level drops, so does the secretion of insulin from the pancreas.
The liver acts as a glucose storage and manufacturing center. When insulin levels are low — when you haven't eaten in a while, for example — the liver converts stored glycogen back to glucose to keep your blood glucose level within a normal range.
In type 1 diabetes, none of this occurs because there's no insulin to let glucose into the cells. So instead of being transported into your cells, sugar builds up in your bloodstream, where it can cause life-threatening complications.
The cause of type 1 diabetes is different from the cause of the more familiar type 2 diabetes. In type 2 diabetes, the islet cells are still functioning, but the body becomes resistant to insulin or the pancreas doesn't produce enough insulin.
There aren't many known risk factors for type 1 diabetes, though researchers continue to find new possibilities. Some known risk factors include:
- A family history. Anyone with a parent or sibling with type 1 diabetes has a slightly increased risk of developing the condition.
- Genetics. The presence of certain genes indicates an increased risk of developing type 1 diabetes. In some cases — usually through a clinical trial — genetic testing can be done to determine if someone who has a family history of type 1 diabetes is at increased risk of developing the condition.
- Geography. The incidence of type 1 diabetes tends to increase as you travel away from the equator. People living in Finland and Sardinia have the highest incidence of type 1 diabetes — about two to three times higher than rates in the United States and 400 times that of people living in Venezuela.
Possible risk factors for type 1 diabetes include:
- Viral exposure. Exposure to Epstein-Barr virus, coxsackievirus, mumps virus or cytomegalovirus may trigger the autoimmune destruction of the islet cells, or the virus may directly infect the islet cells.
- Low vitamin D levels. Research suggests that vitamin D may be protective against type 1 diabetes. However, early intake of cow's milk — a common source of vitamin D — has been linked to an increased risk of type 1 diabetes.
- Other dietary factors. Omega-3 fatty acids may offer some protection against type 1 diabetes. Drinking water that contains nitrates may increase the risk. Additionally, the timing of the introduction of cereal into a baby's diet may affect his or her risk of type 1 diabetes. One clinical trial found that between ages 3 and 7 months appears to be the optimal time for introducing cereal.
Some other possible risk factors include if your mother was younger than age 25 when she gave birth to you or if your mother had preeclampsia during pregnancy. Being born with jaundice or experiencing a respiratory infection just after you were born are also potential risk factors.
Type 1 diabetes can affect many major organs in your body, including your heart, blood vessels, nerves, eyes and kidneys. Keeping your blood sugar level close to normal most of the time can dramatically reduce the risk of many complications.
Long-term complications of type 1 diabetes develop gradually, over years. The earlier you develop diabetes — and the less controlled your blood sugar — the higher the risk of complications. Eventually, diabetes complications may be disabling or even life-threatening.
- Heart and blood vessel disease. Diabetes dramatically increases your risk of various cardiovascular problems, including coronary artery disease with chest pain (angina), heart attack, stroke, narrowing of the arteries (atherosclerosis) and high blood pressure. In fact, about 65 percent of people who have diabetes die of some type of heart or blood vessel disease.
- Nerve damage (neuropathy). Excess sugar can injure the walls of the tiny blood vessels (capillaries) that nourish your nerves, especially in the legs. This can cause tingling, numbness, burning or pain that usually begins at the tips of the toes or fingers and gradually spreads upward. Poorly controlled blood sugar could cause you to eventually lose all sense of feeling in the affected limbs. Damage to the nerves that control digestion can cause problems with nausea, vomiting, diarrhea or constipation. For men, erectile dysfunction may be an issue.
- Kidney damage (nephropathy). The kidneys contain millions of tiny blood vessel clusters that filter waste from your blood. Diabetes can damage this delicate filtering system. Severe damage can lead to kidney failure or irreversible end-stage kidney disease, requiring dialysis or a kidney transplant.
- Eye damage. Diabetes can damage the blood vessels of the retina (diabetic retinopathy), potentially leading to blindness. Diabetes also increases the risk of other serious vision conditions, such as cataracts and glaucoma.
- Foot damage. Nerve damage in the feet or poor blood flow to the feet increases the risk of various foot complications. Left untreated, cuts and blisters can become serious infections. Severe damage might require toe, foot or even leg amputation.
- Skin and mouth conditions. Diabetes may leave you more susceptible to skin problems, including bacterial and fungal infections. Gum infections also may be a concern, especially if you have a history of poor dental hygiene.
- Osteoporosis. Diabetes may lead to lower than normal bone mineral density, increasing your risk of osteoporosis.
- Pregnancy complications. High blood sugar levels can be dangerous for both the mother and the baby. The risk of miscarriage, stillbirth and birth defects are increased when diabetes isn't well controlled. For the mother, diabetes increases the risk of diabetic ketoacidosis, diabetic eye problems (retinopathy), pregnancy-induced high blood pressure and preeclampsia.
- Hearing problems. Hearing impairments occur more often in people with diabetes.
In June 2009, an international committee composed of experts from the American Diabetes Association, the European Association for the Study of Diabetes and the International Diabetes Federation recommended that type 1 diabetes testing include the:
- Glycated hemoglobin (A1C) test. This blood test indicates your average blood sugar level for the past two to three months. It works by measuring the percentage of blood sugar attached to hemoglobin, the oxygen-carrying protein in red blood cells. The higher your blood sugar levels, the more hemoglobin you'll have with sugar attached. An A1C level of 6.5 percent or higher on two separate tests indicates you have diabetes. A result between 6 and 6.5 percent is considered prediabetes, which indicates a high risk of developing diabetes.
If the A1C test isn't available, or if you have certain conditions that can make the A1C test inaccurate — such as if you're pregnant or have an uncommon form of hemoglobin (known as a hemoglobin variant) — your doctor may use the following tests to diagnose diabetes:
- Random blood sugar test. A blood sample will be taken at a random time. Blood sugar values are expressed in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). Regardless of when you last ate, a random blood sugar level of 200 mg/dL (11.1 mmol/L) or higher suggests diabetes, especially when coupled with any of the signs and symptoms of diabetes, such as frequent urination and extreme thirst.
- Fasting blood sugar test. A blood sample will be taken after an overnight fast. A fasting blood sugar level less than 100 mg/dL (5.6 mmol/L) is normal. A fasting blood sugar level from 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is considered prediabetes. If it's 126 mg/dL (7 mmol/L) or higher on two separate tests, you have diabetes.
If you're diagnosed with diabetes, your doctor will also run blood tests to check for autoantibodies that are common in type 1 diabetes. These tests help your doctor distinguish between type 1 and type 2 diabetes. The presence of ketones — byproducts from the breakdown of fat — in your urine also suggests type 1 diabetes, rather than type 2.
After the diagnosis
Once you've been diagnosed with type 1 diabetes, you'll regularly visit your doctor to ensure good diabetes management. During these visits, the doctor will also check your A1C levels. Your target A1C goal may vary depending on your age and various other factors, but the American Diabetes Association generally recommends that A1C levels be below 7 percent, which translates to an estimated average glucose of 154 mg/dL (8.5 mmol/L).
Compared with repeated daily blood sugar tests, A1C testing better indicates how well your diabetes treatment plan is working. An elevated A1C level may signal the need for a change in your insulin regimen or meal plan.
In addition to the A1C test, the doctor will also take blood and urine samples periodically to check your cholesterol levels, thyroid function, liver function and kidney function and to test for celiac disease. The doctor will also examine you to assess your blood pressure, and he or she will check the sites where you test your blood sugar and deliver insulin.