Diabetes is a condition that causes patients to have elevated levels of glucose in the blood due to problems with insulin, which helps regulate blood glucose levels. There are two kinds of diabetes: Type 1 is marked by a lack of insulin production whereas Type 2 is caused by resistance to insulin. There are a number of tests that can be used to diagnose diabetes.
Blood Glucose Testing
One of the primary ways in which patients are tested for diabetes is via the testing of the amount of glucose in their blood. There are two kinds of blood glucose tests that can be performed to diagnose diabetes. Because food intake can cause an increase in blood glucose levels, patients may have their fasting blood glucose measured. The fasting blood glucose is the amount of glucose in the patient's blood when the patient has not eaten for at least eight hours. Another test, called the oral glucose tolerance test, is more sensitive, the National Institute of Diabetes and Digestive and Kidney Disorders explains, but it is also more difficult to administer. Essentially, a patient's fasting blood glucose is measured and then the patient consumes a set amount of glucose. The patient's blood glucose is then measured repeatedly over the course of the next three hours.
Results
Normally people have fasting blood glucose levels that are below 100 mg per dL of blood, explains the National Institute of Diabetes and Digestive and Kidney Disorders. Patients with levels between 100 and 125 mg per dL are considered to have pre-diabetes, whereas levels above that are indicative of diabetes. Similarly, two hours into an oral glucose tolerance test, patients with normal insulin levels have blood glucose levels below 140 mg per dL. Patients with pre-diabetes will have levels between 140 and 199 mg per dL, whereas diabetics will have levels above 200 mg per dL of blood.
Pre-Diabetes vs. Diabetes
Diabetes screening tests that measure blood glucose levels often make a distinction between diabetes and pre-diabetes. Patients with diabetes have blood sugar levels that are high enough that they can cause other complications, such as damage to the kidneys, blood vessels and retinas. Patients with pre-diabetes, which is also known as impaired glucose tolerance, have elevated amounts of glucose in their blood but not to the point where it can cause other health problems. These patients do, however, have a greatly increased risk of developing diabetes.
Hemoglobin A1c
Another test that can be done to diagnose diabetes is called the hemoglobin A1c test. Hemoglobin is a protein that helps transport oxygen throughout the blood. Hemoglobin can react with glucose to form hemoglobin A1c. Because hemoglobin molecules stay in the body for up to three months, the amount of hemoglobin A1c reflects a patient's average blood glucose levels for the previous three months. Normally, 5 percent of all hemoglobin molecules in the blood are A1c. Patients with A1c levels between 6 and 6.5 percent have pre-diabetes; levels above this are indicative of diabetes.
Genetic Testing
Type 1 diabetes typically affects patients early in life as their immune system attacks the cells within the pancreas, whereas Type 2 diabetes is marked by later onset and the gradual development of resistance to insulin. Because Type 1 diabetes occurs early in life, it has a strong genetic component. Children who have parents or siblings with Type 1 diabetes can have genetic testing performed to see whether they are at a high risk of developing Type 1 diabetes. Patients who have one of two genes, known as DR3 and DR4, have an increased chance of developing diabetes, GeneticHealth notes.
