A1C home test: what it shows, the ranges, and its limits
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- Instant A1C finger stick test system. Best for: A quick reading between doctor visits. See options on Amazon
- Mail-in A1C lab test kit. Best for: People who prefer a lab-analyzed sample. See options on Amazon
What the A1C test measures
NIDDK explains that glucose attaches to hemoglobin, the part of a red blood cell that carries oxygen. The higher your blood glucose, the more glucose attaches, and the A1C test measures the amount of hemoglobin with attached glucose. The result is reported as a percentage, and the higher the percentage, the higher your blood glucose has been.
MedlinePlus adds that the test reflects about three months because glucose sticks to hemoglobin for as long as red blood cells are alive, and red blood cells live about three months. A home glucose meter, by contrast, shows your level at a single moment; see our glucose meter kit guide.
A1C ranges
| Result | A1C level | What NIDDK says |
|---|---|---|
| Normal | Below 5.7 percent | A normal A1C level |
| Prediabetes | 5.7 to 6.4 percent | The higher the A1C in this range, the greater the risk of diabetes |
| Diabetes | 6.5 percent or above | Needs confirmation with a second test unless there are clear symptoms |
MedlinePlus lists the same cutoffs and says the ranges are just a guide; what is normal for you depends on your health, age and other factors.
Home results are not a diagnosis
NIDDK says that when the A1C test is used for diagnosis, your doctor sends a blood sample taken from a vein to a lab that uses an NGSP-certified method. It says samples analyzed in a doctor's office or clinic, known as point-of-care tests, should not be used for diagnosis, and that if the A1C shows diabetes or prediabetes without symptoms, you should have a repeat test on a different day to confirm.
A home kit can flag a number worth discussing. NIDDK also notes the A1C should not be used to diagnose type 1 diabetes, gestational diabetes or cystic fibrosis related diabetes.
Who should get an A1C test
MedlinePlus says the CDC recommends A1C testing for diabetes and prediabetes if you are over age 45, or under 45 and more likely to develop diabetes because you have prediabetes, are overweight or have obesity, have a parent or sibling with type 2 diabetes, have high blood pressure or high cholesterol, are physically active less than 3 times a week, have had gestational diabetes, or have polycystic ovarian syndrome. It also lists symptoms that may call for a test, such as feeling very thirsty, urinating a lot, losing weight without trying, feeling very hungry and blurred vision.
If your results show prediabetes, MedlinePlus says you will usually need testing every 1 to 2 years. Talk with your doctor about whether you should be tested.
What can skew an A1C result
- Red blood cell changes. NIDDK lists recent blood loss, sickle cell disease, erythropoietin treatment, hemodialysis and transfusion.
- Low iron. A falsely high A1C can occur in people very low in iron, such as those with iron-deficiency anemia.
- Kidney failure or liver disease can also cause false results, NIDDK says.
- Hemoglobin variants. NIDDK says people of African, Mediterranean or Southeast Asian descent, or with family members with sickle cell anemia or a thalassemia, may have a variant that interferes with some A1C tests.
- Medicines and pregnancy. MedlinePlus says some medicines such as opioids and some HIV medicines may affect results, and to tell your provider if you are pregnant.
Precision and timing
NIDDK says a repeat A1C can be slightly higher or lower than the first: an A1C reported as 6.8 percent could come back anywhere from 6.4 to 7.2 percent on a repeat test of the same sample. Small differences between home results are expected.
You do not have to fast for an A1C test, NIDDK says. The test does not show sudden, temporary rises or drops, and blood glucose in the past 30 days has a greater effect on the reading than earlier months.
If you have diabetes
NIDDK says experts recommend that people with diabetes have an A1C test at least twice a year, and more often if they are not meeting treatment goals. Some people can reduce the risk of complications by keeping A1C below 7 percent, but NIDDK says that target may not be safe if it leads to low blood glucose, and a goal between 7 and 8 percent may suit some people. Discuss your target with your health care professional.
Daily checks still matter between A1C tests; see our continuous glucose monitor guide and ketone meter guide.
What to look for when you buy
Instant A1C finger stick test system
Best for: A quick reading between doctor visits
Gives a percentage you can compare against NIDDK's normal, prediabetes and diabetes ranges.
Watch out: Not for diagnosis; NIDDK says diagnosis uses a lab-certified vein sample.
See options on AmazonMail-in A1C lab test kit
Best for: People who prefer a lab-analyzed sample
Sends a finger stick sample to a lab rather than reading it at home.
Watch out: Still confirm any high result with your health care professional.
See options on AmazonQuestions people ask
- What is a normal A1C?
- NIDDK lists a normal A1C as below 5.7 percent.
- Can a home A1C test diagnose diabetes?
- No. NIDDK says diagnosis uses a vein sample sent to a lab with an NGSP-certified method.
- Do I need to fast for an A1C test?
- No. NIDDK says you do not have to fast for an A1C test.
- Why might my A1C be wrong?
- Anemia, blood loss, transfusion, kidney or liver disease and hemoglobin variants can affect results, NIDDK says.
- How often should people with diabetes check A1C?
- NIDDK says experts recommend at least twice a year, more often if goals are not being met.
Sources
- The A1C Test & Diabetes (niddk.nih.gov), National Institute of Diabetes and Digestive and Kidney Diseases
- Hemoglobin A1C (HbA1c) Test (medlineplus.gov), MedlinePlus, U.S. National Library of Medicine