HbA1c test: normal range and what the result means

As glucose circulates in the blood, some of it attaches to the haemoglobin inside red blood cells — this is glycated haemoglobin, HbA1c. The more glucose there is in the blood, the larger the share of haemoglobin that ends up glycated. Because red blood cells live for about 3 months, HbA1c shows the average glucose level over that period rather than the value on one particular morning. That is why HbA1c is used both to diagnose diabetes and to monitor its control.

The result is reported as a percentage or in mmol/mol (IFCC units) — Lithuanian laboratories often give both. Conditions that change the lifespan of red blood cells — anaemia, haemoglobin variants, kidney or liver disease, pregnancy — can distort the result.

• To diagnose diabetes or prediabetes, when fasting glucose is raised or there are risk factors
• In people with diabetes — to monitor control, usually every 3–6 months
• As a preventive check in adults with excess weight, raised blood pressure or diabetes in the family
• When the fasting glucose test is unreliable because of stress or acute illness

A raised HbA1c means the average amount of glucose in the blood over the last 2–3 months was higher than usual: 5.7–6.4% corresponds to prediabetes, and 6.5% and above to the diabetes criterion. Anaemia, haemoglobin variants and kidney or liver disease can distort the result, so a doctor assesses it together with a glucose test and a complete blood count.

• Prediabetes — average glucose is already raised but has not yet reached the diabetes limit
• Diabetes mellitus (type 1 or type 2)
• Insufficient control of already diagnosed diabetes
• Conditions that prolong the lifespan of red blood cells or alter haemoglobin — these can raise the result artificially

What a doctor usually looks at alongside a raised result:

• A fasting glucose test for confirmation — a diagnosis is not made from a single result
• Whether there is anaemia, or kidney or liver disease, that would distort HbA1c
• Risk factors and lifestyle changes worth discussing
• When to repeat the test to assess the change

A low HbA1c rarely causes concern in itself — it may simply mean a low average glucose. However, conditions that shorten the lifespan of red blood cells (blood loss, haemolysis, some anaemias) lower HbA1c artificially, so the result may not reflect the true glucose level. In people with diabetes, a very low HbA1c may point to frequent episodes of hypoglycaemia.

• Recent blood loss or a blood transfusion
• Haemolysis or other anaemias that shorten the lifespan of red blood cells
• In people with diabetes — overly intensive glucose control with episodes of hypoglycaemia

What a doctor usually looks at alongside a low result:

• A complete blood count and reticulocytes — whether there is anaemia distorting the result
• In diabetes — whether episodes of low blood sugar occur
• Whether HbA1c matches the glucose measurements

HbA1c up to 5.7%

HbA1c up to 5.7% (about 39 mmol/mol) is normal by the American Diabetes Association (ADA) criteria — the average amount of glucose in the blood over the last 2–3 months shows no signs of prediabetes or diabetes. That does not mean there are no risk factors at all, if they appear in other tests or in the family history — a doctor assesses the overall picture.

The ADA defines the normal limit as an HbA1c below 5.7%, which means the average glucose in the blood over the last 2–3 months reached neither the prediabetes range (5.7–6.4%) nor the diabetes limit (6.5% and above). Because HbA1c reflects an average over a longer period rather than a single moment, a result in this band shows that glucose control has been steady over the past months, not merely that glucose happened to be normal on the day of the last measurement.

A normal result does not mean that further testing is unnecessary for everyone — if there are other risk factors (excess weight, diabetes in the family, raised blood pressure), a doctor may keep monitoring the marker periodically. HbA1c can rise slowly over several years before it reaches the prediabetes limit. Healthy adults without risk factors usually need no additional monitoring.

As in the other HbA1c bands, the result can be affected by conditions that change the lifespan of red blood cells — anaemia, haemoglobin variants, recent blood loss, pregnancy. In such cases even a normal HbA1c may not reflect the true average glucose, so a doctor assesses it together with the other findings.

• Additional testing is usually not needed if there are no other risk factors or symptoms
• With excess weight, diabetes in the family or raised blood pressure — periodic HbA1c monitoring with a doctor
• Whether there are conditions that could distort the result — anaemia, a haemoglobin variant, recent blood loss
• An overall assessment of lifestyle and other risk factors together with a doctor

Common questions about this band. Is an HbA1c of 5.5% good? Yes, 5.5% (about 37 mmol/mol) falls within the ADA normal limit (less than 5.7%) and shows no signs of prediabetes or diabetes. Does a normal HbA1c mean there is no diabetes risk at all? A normal result shows that average glucose has not been raised over the last 2–3 months, but the overall future risk is assessed by a doctor together with other factors — weight, family history, blood pressure. How many mmol/mol is an HbA1c up to 5.7%? By the IFCC conversion that is approximately up to 39 mmol/mol; Lithuanian laboratories usually give both units on the report.

HbA1c 5.7–6.4% (about 39–46 mmol/mol) corresponds to prediabetes by the American Diabetes Association (ADA) criteria — a state in which the average amount of glucose in the blood over the last 2–3 months already exceeds normal but does not yet reach the diabetes limit. This is not a diabetes diagnosis; it is a signal to discuss risk factors and a repeat test with a doctor.

The ADA defines prediabetes as an intermediate state between normal and diabetes: average glucose in the blood has already risen above 5.7%, but does not yet reach the 6.5% diabetes limit. Because HbA1c reflects a 2–3 month average rather than one morning's result, a single value in this range shows a trend rather than a sudden change — which is why the guidelines recommend confirming it with a repeat test instead of interpreting it in isolation.

When a result in this range is found, a fasting glucose test or a glucose tolerance test usually follows, so that the picture is fuller, as well as a repeat HbA1c after a few months — to see whether the value is rising, stable or returning to normal. A doctor also reviews the other risk factors — body mass index, blood pressure, the lipid profile, diabetes in the family — because the meaning of prediabetes is assessed in the overall context, not in isolation.

It also matters that HbA1c can be inaccurate in anaemia, with a haemoglobin variant or in kidney disease — in such cases the result can deviate from the true average glucose, so a doctor compares it with other tests before drawing conclusions.

• A repeat HbA1c or a fasting glucose test after a few months, to assess the change
• A glucose tolerance test, if a more precise picture is needed
• Other risk factors — body mass index, blood pressure, the lipid profile, diabetes in the family
• Whether there are conditions that could distort HbA1c — anaemia, or kidney or liver disease

Common questions about this band. Does an HbA1c of 6.0% mean diabetes? No. 6.0% (about 42 mmol/mol) falls within the ADA prediabetes range (5.7–6.4%), not the diabetes criterion, which starts at 6.5%. How does prediabetes differ from diabetes by HbA1c? By ADA, prediabetes is 5.7–6.4%, and the diabetes criterion starts at 6.5%; the limit is set by the statistical relationship with the risk of complications, not by any single symptom. How many mmol/mol is an HbA1c of 5.7–6.4%? By the IFCC conversion, approximately 39–46 mmol/mol; Lithuanian laboratories usually give both units on the report. Can a prediabetes value return to normal? A repeat test may show a different value depending on lifestyle changes and other factors — how to interpret that in an individual case is decided by a doctor.

HbA1c 6.5% and above

HbA1c 6.5% (about 48 mmol/mol) and above meets the American Diabetes Association (ADA) criterion for diagnosing diabetes. It means the average amount of glucose in the blood over the last 2–3 months was persistently high. This result on its own does not confirm a diagnosis — a doctor assesses it together with other tests, symptoms and, if needed, a repeat measurement.

The ADA states that an HbA1c of 6.5% or more meets the diabetes diagnostic limit; however, if there are no clear symptoms or very high glucose, the diagnosis is usually confirmed by a second test on another day, or by a different type of test — for example fasting glucose. This reduces the chance that a one-off laboratory error or a temporary condition leads to a wrong conclusion.

When a value in this range is found, a doctor usually also assesses the other markers related to diabetes risk and its consequences — blood pressure, the lipid profile, kidney function (creatinine, GFR). Together these markers help build an overall picture of health and plan further tests.

As in the other HbA1c bands, the result can be distorted by anaemia, haemoglobin variants, recent blood loss or a transfusion, or kidney or liver disease — in such cases a doctor may rely more on direct glucose measurements than on a single HbA1c result.

• A repeat test for confirmation, if the first result came without clear symptoms
• A fasting glucose test for additional confirmation
• An assessment of kidney function, the lipid profile and blood pressure
• Whether there are conditions that could distort HbA1c — anaemia, kidney or liver disease, recent blood loss

Common questions about this band. Does an HbA1c of 6.5% automatically mean diabetes? It meets the ADA diabetes diagnostic limit, but the diagnosis is usually confirmed by a second test, or by a doctor's assessment together with symptoms. Is an HbA1c of 7% high? 7% (about 53 mmol/mol) is above the ADA diabetes limit (6.5%); what it means in an individual case is assessed by a doctor together with other tests. How many mmol/mol is an HbA1c of 6.5%? By the IFCC conversion, approximately 48 mmol/mol — Lithuanian laboratories often give this value next to the percentage. Does one high HbA1c result always mean diabetes? Not always — the result can be distorted by anaemia or other conditions, so the ADA recommends confirmation with a second test if there are no clear diabetes symptoms.

Related indicators in English: blood glucose, glucose tolerance test, haemoglobin, creatinine, complete blood count.

At the Medicina practica laboratory in Lithuania, an HbA1c test costs from €13 (September 2026 pricing).