A1c, also called hemoglobin A1c, is a blood test that measures the level of glycosolated hemoglobin in a person's blood. This is a common test ordered for people with diabetes or people suspected of having diabetes. It gives the doctor an idea of a person's average blood sugar, or blood glucose levels, over the prior three to four months. It does not replace daily blood glucose monitoring, but in combination with daily readings, the test helps the doctor determine how well a current diabetes treatment plan is working.
Glycosolated hemoglobin is found in everyone's blood in small amounts. It is a compound that forms when glucose molecules bond with hemoglobin, or red blood cells. Once this bond is formed, it does not break down, but remains in the bloodstream. Hemoglobin cells live for approximately 120 days, so at the time the test is performed, it will measure the amount of hemoglobin that has attached to glucose over the last three to four months. When more glucose is in the blood, more A1c is formed, so elevated levels of A1c indicate that daily blood glucose levels have also been elevated over this time period.
Diabetes treatment plans strive to keep a patient's blood sugar within normal limits and reduce the risks associated with high blood sugar, which include blindness, kidney damage, and nerve damage in the arms and legs. Daily blood glucose readings will give the patient an immediate idea of his blood glucose levels, which helps the patient make immediate corrections in diet or medication, as directed by their doctor. In addition to daily monitoring, doctors use the test to get an overview of how well the current treatment plan is working. It may help a doctor decide whether a patient needs insulin and how much is needed. If a doctor suspects diabetes in a patient who has not yet been diagnosed, the test is sometimes used as a diagnostic tool, indicating whether the patient has had elevated blood glucose over the prior three to four months.
Scientists discovered the A1c compound in 1967, and the American Diabetes Association, or ADA, began recommending routine testing of A1c levels for diabetic patients in 1988. In a person without diabetes, the normal range of A1c in the blood is 4-6%. Levels above 7% indicate that a current treatment plan may not be working effectively. The ADA recommends testing levels every four months for diabetic patients who use insulin, and every two months for diabetic patients who are not using insulin. Your doctor will use this and other tests to determine the treatment plan that is best for you.