HbA1c: what your value means

The key points

HbA1c (long-term blood sugar) shows how your blood sugar has averaged over the past two to three months, independent of individual days and meals.
Common Swedish reference intervals are 27 to 42 mmol per mol for adults under 50 and 31 to 46 mmol per mol from age 50.
Values between 42 and 47 mmol per mol count as a risk zone for type 2 diabetes and are usually followed up.
48 mmol per mol and above is the level used in diagnosing diabetes, but a diagnosis requires repeat testing and is always made by a doctor.
An HbA1c below 48 does not rule out diabetes, since anemia and certain hemoglobin variants, among other things, can affect the value.

What is HbA1c?

HbA1c (long-term blood sugar) measures how large a share of the hemoglobin in your red blood cells has sugar bound to it. Because red blood cells live for around three months, the value becomes an average of your blood sugar over the past two to three months.

That is what makes the value so useful. A single glucose reading is colored by your last meal, the night and the moment, while HbA1c shows the trend. In Sweden the value is reported in mmol per mol, and it is the same measure healthcare uses both to find diabetes and to follow those who already have the diagnosis.

HbA1c table: what does your value mean?

This is how HbA1c is read in Swedish healthcare, according to Läkemedelsboken and Swedish laboratories' test instructions.

HbA1c, mmol per mol	What it usually means
27 to 42	Reference interval for adults under 50
31 to 46	Reference interval for adults 50 and over
42 to 47	Risk zone for type 2 diabetes, usually followed up
48 and above	Level used in diagnosing diabetes, requires a doctor's assessment

One important nuance: the diagnostic threshold of 48 is different from the upper limit of the reference interval. Swedish practice requires two samples with HbA1c at 48 or more, or one such value combined with elevated glucose, before diabetes is diagnosed. A single value, wherever it lands, is a signal to follow up on, never a verdict in itself.

What is the difference between HbA1c and blood sugar?

Glucose is the snapshot, HbA1c is the trend. A fasting glucose shows where your blood sugar sits that particular morning and is reported in mmol per liter. Under the WHO criteria applied in Swedish healthcare, the diagnostic threshold for diabetes is a fasting glucose of 7.0 mmol per liter or more, confirmed by a second sample, while values between 6.1 and 6.9 count as elevated.

The two measures complement each other. A normal fasting glucose can coexist with an HbA1c that has been creeping upward, and the reverse happens too. That is why they are often measured together, and why both are used when healthcare investigates suspected diabetes.

Can HbA1c be misleading?

Yes, in certain situations. Because the value is built on the lifespan of red blood cells, anything that changes that lifespan can affect the number. Anemia, larger blood losses, certain inherited hemoglobin variants and pregnancy can make HbA1c fail to reflect the true blood sugar.

For the same reason, the WHO stresses that a value below 48 mmol per mol does not rule out diabetes. With symptoms or strong suspicion, healthcare proceeds with glucose measurements even when HbA1c looks fine. A surprising value, in either direction, is a reason to talk to a doctor rather than draw your own conclusions.

How do you test HbA1c?

HbA1c is measured in an ordinary blood test, no referral needed. You walk in to a sampling location when it suits you. The HbA1c value itself requires no fasting, but it is best measured together with a fasting glucose, in which case the sample is taken on an empty stomach so both values read true.

Blood Sugar Status contains that pair, HbA1c for the trend and fasting glucose for the snapshot, plus a lipid profile of total cholesterol, HDL, LDL, non-HDL and triglycerides, 7 results in all. Taken recurringly, yearly for example, the values build your own reference line, making a slow upward drift visible long before it becomes a problem.

When should you see a doctor?

Contact healthcare if your HbA1c sits at 42 mmol per mol or higher, for follow-up and advice, and more promptly at 48 or higher, since that is the level where diabetes needs investigating. Also seek care regardless of your report if you have symptoms like increased thirst, large urine volumes, unexplained weight loss, blurred vision or marked tiredness.

An article can explain what the numbers usually mean, but the diagnosis, and the plan forward, always belongs with a doctor.

Blood Sugar Status measures HbA1c, fasting glucose and a lipid profile, 7 results, no referral needed.

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Common questions

What is a normal HbA1c value?

Common Swedish reference intervals are 27 to 42 mmol per mol for adults under 50 and 31 to 46 mmol per mol from age 50. The interval on your own report is the one that applies to your value.

What does an HbA1c of 42 mean?

42 mmol per mol sits at the upper edge of the reference interval for adults under 50, and the 42 to 47 range counts as a risk zone for type 2 diabetes. It does not mean you have diabetes, but the value is usually followed up, ideally with a doctor.

At what HbA1c do you have diabetes?

The diagnostic level is 48 mmol per mol. Swedish practice requires two samples at 48 or more, or one such value together with elevated glucose, and the assessment is always made by a doctor. At the same time, a value below 48 does not rule diabetes out.

Do you need to fast before an HbA1c test?

Not for the HbA1c value itself, it is unaffected by your last meal. When it is measured together with fasting glucose, as in most blood sugar panels, the whole sample is taken fasting so the glucose value reads true.

How fast can HbA1c change?

The value reflects blood sugar over the past two to three months, so changes appear with that lag. Anyone changing diet, weight or exercise usually sees the effect in HbA1c only after two to three months.