Hemoglobin is the oxygen-carrying part of the red blood cells. This blood test measures a special kind of hemoglobin that has been coated with glucose, the main sugar in the body. It is called glycosylated hemoglobin, hemoglobin A1C, or HbA1C.
Normally, this test is done only on people with diabetes. It is often done at least once or twice a year to see if the diabetes is being controlled. However, many physicians recommend this test every three months.
A blood sample is taken from a vein in the forearm or the hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through the veins.
A very thin needle is gently inserted into a vein and the tourniquet is removed. Blood flows from the vein through the needle and is collected into a syringe or vial. The sample is sent to a lab and analyzed.
After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
Home test kits that can be done with a fingerstick and test strips that are sent to a lab will be available soon. There are also home monitors that measure fructosamine, which is the glycosylation of different blood proteins. Sometimes called the glycoprotein test, this measures control of diabetes over about a 2-week period of time.
No preparation is needed for this test.
The normal range for HbA1C is usually about 4% to 6% in people without diabetes. The goal for people with diabetes is a level of 7% or less of HbA1C. If HbA1C is higher than that, the healthcare provider will often make adjustments in the person's diabetes treatment plan.