It is a disease in which the body’s ability to produce or respond to the hormone insulin is impaired, resulting in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood.
Usually occurs when your blood glucose, also called blood sugar, is too high. Blood glucose is your main source of energy and comes from the food you eat. Insulin, a hormone made by the pancreas, helps glucose from food get into your cells to be used for energy. Sometimes your body doesn’t make enough—or any—insulin or doesn’t use insulin well. Glucose then stays in your blood and doesn’t reach your cells.
Over time, having too much glucose in your blood can cause health problems. Although diabetes has no cure, you can take steps to manage your diabetes and stay healthy.
Different types of diabetes
Type 1 diabetes
If you have type 1 diabetes, your body does not make insulin. Your immune system attacks and destroys the cells in your pancreas that make insulin. Type 1 diabetes is usually diagnosed in children and young adults, although it can appear at any age. People with type 1 diabetes need to take insulin every day to stay alive.
Type 2 diabetes
If you have type 2 diabetes, your body does not make or use insulin well. You can develop type 2 diabetes at any age, even during childhood. However, this type of diabetes occurs most often in middle-aged and older people. Type 2 is the most common type of diabetes.
Prediabetes is when your blood glucose, also called blood sugar, levels are higher than normal, but not high enough to be called diabetes. Having prediabetes is serious because it raises your chance of developing type 2 diabetes. Many of the same factors that raise your chance of developing type 2 diabetes put you at risk for prediabetes.
Gestational diabetes develops in some women when they are pregnant. Most of the time, this type of diabetes goes away after the baby is born. However, if you’ve had gestational diabetes, you have a greater chance of developing type 2 diabetes later in life. Sometimes diabetes diagnosed during pregnancy is actually type 2 diabetes.
Other types of diabetes
Less common types include monogenic diabetes, which is an inherited form of diabetes, and cystic fibrosis-related diabetes.
Diabetes Tests & Diagnosis
Your health care professional can diagnose diabetes, prediabetes and gestational diabetes through blood tests. The blood tests show if your blood glucose, also called blood sugar, is too high. Health care professionals most often use the fasting plasma glucose (FPG) test or the A1C test to diagnose diabetes. In some cases, they may use a random plasma glucose (RPG) test.
Fasting plasma glucose (FPG) test
The FPG blood test measures your blood glucose level at a single point in time. For the most reliable results, it is best to have this test in the morning, after you fast for at least 8 hours. Fasting means having nothing to eat or drink except sips of water.
The A1C test is a blood test that provides your average levels of blood glucose over the past 3 months. Other names for the A1C test are hemoglobin A1C, HbA1C, glycated hemoglobin, and glycosylated hemoglobin test. You can eat and drink before this test. When it comes to using the A1C to diagnose diabetes, your doctor will consider factors such as your age and whether you have anemia or another problem with your blood. The A1C test is not accurate in people with anemia.
If you’re of African, Mediterranean, or Southeast Asian descent, your A1C test results may be falsely high or low. Your health care professional may need to order a different type of A1C test.
Your health care professional will report your A1C test result as a percentage, such as an A1C of 7 percent. The higher the percentage, the higher your average blood glucose levels.
People with diabetes also use information from the A1C test to help manage their diabetes.
Random plasma glucose (RPG) test
Sometimes health care professionals use the RPG test to diagnose diabetes when diabetes symptoms are present and they do not want to wait until you have fasted. You do not need to fast overnight for the RPG test. You may have this blood test at any time.
Tests to diagnose gestational diabetes
Pregnant women may have the glucose challenge test, the oral glucose tolerance test, or both. These tests show how well your body handles glucose.
Glucose challenge test
If you are pregnant and a health care professional is checking you for gestational diabetes, you may first receive the glucose challenge test. Another name for this test is the glucose screening test. In this test, a healthcare professional will draw your blood 1 hour after you drink a sweet liquid containing glucose. You do not need to fast for this test. If your blood glucose is too high—135 to 140 or more—you may need to return for an oral glucose tolerance test while fasting.
Oral glucose tolerance test (OGTT)
The OGTT measures blood glucose after you fast for at least 8 hours. First, a health care professional will draw your blood. Then you will drink the liquid containing glucose. For diagnosing gestational diabetes, you will need your blood drawn every hour for 2 to 3 hours.
High blood glucose levels at any two or more blood test times during the OGTT—fasting, 1 hour, 2 hours, or 3 hours—mean you have gestational diabetes. Your health care team will explain what your OGTT results mean.
Healthcare professionals also can use the OGTT to diagnose type 2 diabetes and prediabetes in people who are not pregnant. The OGTT helps healthcare professionals detect type 2 diabetes and prediabetes better than the FPG test. However, the OGTT is a more expensive test and is not as easy to give. To diagnose type 2 diabetes and prediabetes, a healthcare professional will need to draw your blood 1 hour after you drink the liquid containing glucose and again after 2 hours.
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. Oral glucose tolerance test. For this test, you fast overnight, and the fasting blood sugar level is measured.