HbA1c

HbA1c (glycated haemoglobin) shows average blood sugar over the last two to three months. It is used to detect diabetes and prediabetes and to monitor treatment in people with diabetes. Fasting is not required.

Who the test is for

• people with increased thirst, frequent urination, persistent fatigue, unexplained weight loss or frequent infections;
• people with excess weight, a family history of diabetes, high blood pressure or blood lipids;
• people with previous prediabetes or women who had diabetes during pregnancy (gestational diabetes);
• people whose glucose is borderline or raised when fasting;
• people with diabetes, to monitor treatment, usually every three to six months.

What HbA1c is and what it shows

Haemoglobin is the protein in red blood cells carrying oxygen. Blood glucose binds permanently to part of haemoglobin, increasingly as blood sugar rises. Red blood cells live around 120 days, so glycated haemoglobin reflects average glucose during that period, with recent weeks having the greatest influence.

Glucose shows the situation at collection, while HbA1c does not change because of one meal, stress or dieting for several days before testing. HbA1c is reported in mmol/mol (IFCC units) and percentages (%).

Panels including this test

Test HbA1c is also included in this panel.

Glycaemic status panelblood glucose, HbA1c16.00€Details ›

All panels including HbA1c (12) ›

Preparation and sample

The sample is venous blood. Fasting is unnecessary for HbA1c alone and blood can be collected at any time of day. If glucose is measured simultaneously, for example in the Glycaemic status panel, come in the morning fasting after 8 to 12 hours without food; plain water is permitted.

How to interpret the result

For adults other than pregnant women, the American Diabetes Association (ADA) and World Health Organization (WHO) use these thresholds:

Result	HbA1c (mmol/mol)	HbA1c (%)
normal	below 39	below 5,7
prediabetes (according to ADA)	39–47	5,7–6,4
diabetes	48 or higher	6,5 or higher

Some guidelines, such as UK NICE guidance, define increased risk only from 42 mmol/mol (6,0 %), so different thresholds can appear on reports. Without clear symptoms, diabetes is diagnosed only when two results are raised, for example repeat HbA1c or HbA1c and fasting glucose. Read more about criteria in The role of HbA1c testing in diagnosing diabetes.

For people treated for diabetes, the target for most adults is HbA1c below 53 mmol/mol (7 %). A doctor still sets it individually according to age, other diseases and susceptibility to hypoglycaemia.

HbA1c can be falsely raised or lowered in anaemia, after major blood loss or transfusion, with some inherited haemoglobin variants, advanced kidney disease and pregnancy. A doctor then relies more on glucose and glucose tolerance testing. A doctor always interprets results alongside symptoms and other findings.

Glycaemic status: HbA1c and glucose together

Glycaemic status refers to measuring fasting blood glucose (GUK) and HbA1c together. Glucose shows blood sugar at collection while HbA1c reflects the average over recent months, so the tests complement each other. If either is in the prediabetes or diabetes range, a doctor can request repeat testing or a glucose tolerance test.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed under Contact). Prices for all tests and panels are available in the service price list. Fasting glucose and HbA1c from the same sample can be measured as the Glycaemic status panel.

Frequently asked questions

What does raised HbA1c mean?

That average blood sugar has been higher than normal over recent months. A value of 39 to 47 mmol/mol (5,7–6,4 %) suggests prediabetes, while 48 mmol/mol (6,5 %) or higher suggests diabetes, confirmed by a doctor using repeat or another test.

What are normal HbA1c values?

The report’s upper reference limit is usually around 42 mmol/mol (6,0 %), with the precise interval printed on your report. The interval differs from a diagnostic threshold: ADA values from 39 mmol/mol (5,7 %) already suggest prediabetes, so a result within the interval can exceed that threshold. A doctor makes the diagnosis according to guidelines.

Can HbA1c replace blood glucose meter measurements?

No. HbA1c shows an average but does not reveal daily sugar spikes or falls. People treated with insulin still need self-monitoring with a glucose meter or sensor as directed by a doctor; HbA1c complements it.

When should HbA1c be repeated?

While diabetes treatment is being adjusted, usually after three months; once values are stable, at least twice a year. Prediabetes is most often checked annually. Because HbA1c changes slowly, repeating it after only a few weeks rarely makes sense.