Home › Biomarkers › HbA1c
The US CDC recommends an HbA1c test for everyone over the age of 45. Even if you are younger, the test can be useful, for example if you are more likely to have blood sugar that is too high.[1]
On this page you can read what glycated haemoglobin is, what the guidelines say about a value that is too low or too high, what affects your value and which values are best to look at alongside it.
Also known as: A1C, glycated haemoglobin, glycohaemoglobin, glycosylated haemoglobin. At the lab: HBA1L.
HbA1c shows how high your blood sugar was on average over the past two to three months. Blood sugar is also called glucose. It is a sugar that comes from your food and that your cells use for energy. A hormone called insulin helps glucose get into your cells.[1]
Glucose in your blood sticks to haemoglobin, a protein in your red blood cells. The higher your blood sugar, the more haemoglobin becomes coated with glucose. The test measures what percentage of your haemoglobin is coated with glucose. Red blood cells live for about three months, and the glucose stays attached for that long.[1]
A high value can point to blood sugar that is too high. For the test, blood is taken from a vein in your arm. A condition of the red blood cells, such as anaemia, can affect the result. The same applies to a disease of the liver or kidneys that no longer work properly.[1]
You don't always notice when your blood sugar is too high. MedlinePlus lists symptoms where the test can be useful: being very thirsty, peeing often, feeling very hungry, blurred vision, tiredness, dry skin and tingling or numb hands or feet.[1]
The test can also be useful if you are under 45. For example, if you are overweight, if a parent, brother or sister has a condition that affects how the body handles sugar, if you have high blood pressure or high cholesterol, or if you exercise less than 3 times a week.[1]
If your value is between 5.7% and 6.4%, you are usually tested again every 1 to 2 years. Ask your doctor how often you need it.[1]
The lab reports HbA1c in mmol/mol. The reference value is 20 to 42 mmol/mol. The lab calls a value between those limits normal.[2]
| Value | What it can mean | Who it is for |
|---|---|---|
| Below 5.7%[1] | Normal | When checking for blood sugar that is too high |
| Between 5.7% and 6.4%[1] | Can point to blood sugar that is higher than normal | When checking for blood sugar that is too high |
| 6.5% or higher[1] | Can point to a condition that affects how your body handles sugar | When checking for blood sugar that is too high |
MedlinePlus: commonly used limits, as a percentage of your haemoglobin. They are a guideline; what is normal for you depends on your health, your age and other factors.[1]
A value between 5.7% and 6.4% can point to blood sugar that is higher than normal, but not yet as high as with a condition that affects how your body handles sugar. A value of 6.5% or higher can point to such a condition. Doctors often use more than one test. After a high result, a new HbA1c test or a fasting glucose test sometimes follows.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Certain medicines, such as opioids and some HIV medicines, can affect your result. Tell your doctor everything you take. Don't stop taking a medicine unless your doctor tells you to.[1]
If you are pregnant, tell your doctor. That can also affect your result.[1]
Your blood sugar changes all the time. A measurement at home shows how high it is at that moment. This test instead gives an average over a longer period.[1]
HbA1c is included in BioProfile 87, 121 and 150.[3]
The BioProfile editorial team wrote this page on 28 October 2026, using the sources below, which we read on 28 October 2026. Every number on this page comes from one of those sources, and the number of that source appears next to it. An expert has yet to review this page. Once that review is done, the expert's name and the date of the review will appear at the top. This page explains, it does not give a diagnosis. Discuss a value outside the normal range with your GP.
