Sugar and metabolism · Blood

HbA1c

Average blood sugar over the last 2 to 3 months; the standard monitoring value in diabetes and internationally also a diagnostic test.

At a glance

Measured in blood
In 12 test panels
No special preparation

Explanation

HbA1c: what is measured?

Glucose in the blood spontaneously attaches to hemoglobin, the red pigment in red blood cells. The higher the average blood sugar, the larger the share of 'sugar-coated' hemoglobin (HbA1c). Because a red blood cell lives for about 3 months, HbA1c reflects the average blood sugar over the preceding 8 to 12 weeks, regardless of what was eaten that morning. The result is given in mmol/mol (formerly as a percentage: 48 mmol/mol corresponds to 6.5 percent).

What can it detect?

Diabetes mellitus: HbA1c of 48 mmol/mol or higher (WHO criterion; the NHG makes the diagnosis with fasting glucose)
Increased risk of diabetes with values just below that cutoff (about 42 to 47 mmol/mol)
How well known diabetes is controlled (target usually 53 mmol/mol or lower)

Result

What does the result mean?

HbA1c too high

An HbA1c of 48 mmol/mol or higher fits diabetes; according to the WHO this counts as diagnostic, provided that in someone without symptoms it is confirmed in a second measurement. The Dutch GP guideline (NHG) has the GP make the diagnosis with fasting glucose, so in the Netherlands a high HbA1c is followed by a fasting glucose measurement. Values of about 42 to 47 mmol/mol mean a raised average blood sugar with a higher chance of diabetes and cardiovascular disease, without diabetes being present yet. With known diabetes, a value above the personal target means that blood sugar has been too high over the past months. A falsely high result occurs with severe kidney failure, after removal of the spleen and with certain hemoglobin variants. A raised HbA1c does not cause symptoms by itself.

HbA1c too low

An HbA1c below the reference value is rare in healthy people and then usually has no significance. In diabetes, a value far below the target points to tight control with a risk of blood sugars that are too low. A falsely low result arises when red blood cells live shorter than normal: after blood loss, with breakdown of blood cells (hemolysis), in the first weeks of iron or vitamin B12 treatment, during pregnancy and with some hemoglobin variants; the average blood sugar is then higher than the result suggests.

After an abnormal result

With an HbA1c of 48 mmol/mol or higher, or just below it, the GP has a fasting glucose measured (twice, on different days) to diagnose or rule out diabetes, and maps out the cardiovascular risk profile. With known diabetes, the treatment is adjusted if needed and the HbA1c is repeated at set times.

Reliability

How reliable is the test?

HbA1c is a well-standardized test with little influence from food, stress or time of day; it is the standard monitoring value in diabetes. For detecting diabetes the picture is more nuanced: the WHO and many countries use 48 mmol/mol or higher as a diagnostic criterion, but HbA1c finds fewer people with diabetes than glucose does: in the New Hoorn Study, at a cutoff of 48 mmol/mol, only 24 percent of people with diabetes according to the glucose tolerance test had a raised HbA1c, at a specificity of 99 percent. A raised HbA1c is therefore a strong indication; a normal HbA1c does not rule out diabetes. That is why in the Netherlands the diagnosis is made with fasting glucose.

What can affect the result?

Anything that changes the lifespan of red blood cells disturbs the result: blood loss, hemolysis, pregnancy and a recently started iron or B12 treatment (falsely low); a removed spleen and severe kidney failure (falsely high).
Hemoglobin variants such as sickle cell and thalassemia carriership, more common in people with a non-Western background, can make the measurement unreliable; the diagnosis must then be made on glucose.
HbA1c lags behind: a blood sugar that has only recently risen (for example due to prednisone or diabetes that developed quickly) cannot be seen in it yet.
Age and ethnic background affect the value slightly (differences of 2 to 3 mmol/mol), people differ in the degree to which their proteins become glycated, and the measurement method allows a spread of a few percent.

Who it is for

Who is the test useful for?

Useful for

Useful for monitoring known diabetes and as an additional measure for people at increased risk of diabetes (overweight, diabetes in the family, a previously impaired fasting glucose, previous gestational diabetes) who cannot or do not want to have a fasting blood draw. As a standalone screening test in healthy people without risk factors, HbA1c says less than fasting glucose, because it misses some of the people with diabetes. Not suitable with anemia, hemoglobin variants, pregnancy or a recently developed disturbance of blood sugar.

How common is it?

In 2024, about 1.2 million people in the Netherlands were known to their GP to have diabetes, of whom just over 1.1 million had type 2 (61 per 1000 inhabitants), men more often than women and mainly at older age. According to the Dutch GP guideline (NHG), about 30 percent of people over 60 have a precursor stage of diabetes (impaired fasting glucose or impaired glucose tolerance); at least half of them never develop diabetes.

VZinfo (RIVM) based on Nivel primary care registrations, 2024; the NHG guideline on type 2 diabetes mellitus

Drawbacks and risks

A normal HbA1c can give false reassurance: it misses some of the people who do have diabetes according to the glucose criteria.
A slightly raised value with a hemoglobin variant or after blood loss can cause unnecessary worry.

Get tested

HbA1c: test panels

HbA1c is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Blood draw
HbA1c
HbA1c; average glucose (8–12 weeks).
€ 26,00
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Weight Loss Test
Panel for metabolism and weight; glucose, lipids, and hormones.
€ 89,00
Fingerstick
HbA1c
Average blood sugar (8–12 weeks).
€ 26,00
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InsideTracker
InsideTracker Blood Analysis: analyze 48 biomarkers for complete health optimization and personalized recommendations.
€ 335,00
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Keto Diet
Total cholesterol, HDL, LDL, triglycerides, glucose and HbA1c. For people on a ketogenic diet or considering starting keto.
€ 95,00
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Comprehensive Blood Test
Comprehensive blood test covering blood count, thyroid, kidney and liver function, glucose, inflammation markers and cholesterol.
€ 215,00
Blood draw
Heart Complete Test
Lipid profile, kidney function, glucose, HbA1c, and NT-proBNP cardiac marker. Comprehensive cardiovascular health check.
€ 105,00
Blood draw
Cardio Profile Extensive
Complete lipids, Lipoprotein(a), Apolipoprotein B/A1, kidney function and blood sugar. Advanced cardiovascular risk analysis.
€ 165,00
Blood draw
Cardio Profile Basic
Complete cardiovascular screening with cholesterol, blood sugar, and inflammation marker.
€ 90,00

How reliable is the test?

HbA1c