What is hemoglobin A1c?

Hemoglobin A1c is a test that indicates the average level of blood sugar over the past 2 to 3 months. People with diabetes need to have this test done regularly to see whether their blood sugar levels have been staying within a target range.

Blood for a hemoglobin A1c test can be collected at home or at your doctor's office.

• Home testing. Home test kits for hemoglobin A1c are available. Using the kit, you can use a lancet (a small needle) to take a blood sample from a finger. Then, put a few drops of blood on a sample card. Place the card in an envelope and send it to a lab for testing. The lab sends the results of the test to you or your doctor.
• Doctor's office. Some health professionals, particularly endocrinologists, have blood-analysis equipment in their offices that can test hemoglobin A1c blood levels from a finger stick. The health professional can then review the results during the appointment.
• Laboratory testing. The most accurate measurement of hemoglobin A1c level is done in commercial laboratories. These labs may be run by local hospitals or large health clinics, or they may be independently owned. Lab personnel check their equipment often, calibrate their machines on a regular schedule, and are monitored by federal and state regulatory authorities. A health professional's office sends the blood sample to the lab. How long it takes to get results depends on the lab. You can have the test results reported to you or your doctor.

Hemoglobin A1c test results show your average blood sugar level over time. The result is reported as a percentage. Your goal is to keep your hemoglobin A1c level as close to the normal level as possible. Studies suggest that the lower the hemoglobin A1c level, the lower the incidence of diabetic complications (eye, kidney, heart, blood vessel, and nerve disease). The American Diabetes Association (ADA) recommends keeping the hemoglobin A1c less than 7%. Some people may be able to achieve an even lower level of less than 6%.¹

The table below compares hemoglobin A1c percentages with average blood sugar levels over the previous few months.

Comparison of hemoglobin A1c and blood glucose levels

Hemoglobin A1c %	Average blood glucose (mg/dL)	Average blood glucose (mmol/L)
6%	135	7.5
7%	170	9.5
8%	205	11.5
9%	240	13.5
10%	275	15.5
11%	310	17.5
12%	345	19.5

A1c levels for children and teens are different. For children younger than 6 years old, the ADA recommends an A1c level from 7.5% to 8.5%. In children 6 to 12 years old, the recommended level is less than 8%. And in teens, the recommended level is less than 7.5%.²

Results of hemoglobin A1c tests read at different labs vary, but standardization among labs is improving. There could be differences from one lab to another as great as half a percentage point. For example, if your hemoglobin A1c at one lab is 8%, it may be 8.5% at another lab on the same day.

Citations

1. American Diabetes Association (2007). Standards of medical care in diabetes. Clinical Practice Recommendations 2007. Diabetes Care, 30(Suppl 1): S4–S41.

2. American Diabetes Association (2005). Care of children and adolescents with type 1 diabetes. Diabetes Care, 28(1): 186–212.