Hemoglobin A1c test
The HbA1c test measures the amount of glucose attached to hemoglobin - the oxygen-carrying protein in red blood cells that gives blood its color. The HbA1c test is used in people already diagnosed with diabetes and is not recommended for diagnosing diabetes. As blood glucose levels rise, so does the amount of glucose attached to hemoglobin. Since hemoglobin circulates in the blood until the red blood cells die (half of red blood cells are replaced every 120 days), the HbA1c test measures average blood glucose levels over the previous two to three months.
The American Diabetes Association recommends keeping your HbA1c levels at less than 7 percent, which is equivalent to an average blood glucose level of about 170 mg/dL or less. Your doctor may give you a different level to aim for, depending on your age, weight, and other factors. HbA1c tests are usually performed every three months to see if you are maintaining your blood glucose within the target range. If you have stable blood glucose levels and are meeting your treatment goals, you may need less frequent HbA1c testing.
Other laboratory tests
In addition to measures of blood glucose and HbA1c, initial and subsequent doctor visits may include tests to check for kidney damage, a common complication of diabetes. These tests include blood urea nitrogen (BUN), blood creatinine, and protein (albumin) in the urine. The risk of coronary heart disease is increased in people with diabetes, so you'll also need blood tests to measure levels of triglycerides, total cholesterol, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol.