HbA1c of 6% (42 mmol/mol): what it means for you

An HbA1c of 6.0% is exactly 42 mmol/mol, the unit UK labs use. In the UK it is the first value of the prediabetes range (42–47 mmol/mol); in the US the prediabetes range starts lower, at 5.7% (39 mmol/mol). Either way it is not diabetes, which starts at 6.5% (48 mmol/mol), but it signals a higher risk worth taking seriously. It corresponds to an average blood sugar of about 7.0 mmol/L (126 mg/dL).

Updated: 2026-10-26

Reference ranges

Category	Reference range
Normal, UK	below 42 / below 6.0% mmol/mol (UK) / % (US)
Normal, US (ADA)	below 39 / below 5.7% mmol/mol (UK) / % (US)
Prediabetes, UK (NICE)	42–47 / 6.0–6.4% mmol/mol (UK) / % (US)
Prediabetes, US (ADA)	39–47 / 5.7–6.4% mmol/mol (UK) / % (US)
Diabetes range	48 or more / 6.5% or more mmol/mol (UK) / % (US)

A diagnosis of diabetes without symptoms needs a second confirming test. HbA1c is not reliable in some situations (see below); your doctor will judge which test fits.

What HbA1c measures

Glucose in the blood sticks to haemoglobin inside red cells. Because red cells live about three months, the share of "glycated" haemoglobin reflects your average blood sugar over the past two to three months, with the most recent weeks counting most. You do not need to fast for it.

The same test is reported two ways. The US and many other countries give a percentage (DCCT units); the UK and much of Europe give mmol/mol (IFCC units). 42 mmol/mol = 6.0%, 48 mmol/mol = 6.5%, 53 mmol/mol = 7.0%.

HbA1c 6.0 and 6.1: normal or prediabetes?

This is where the UK and the US genuinely differ. Under NICE and NHS guidance, an HbA1c of 42 to 47 mmol/mol (6.0 to 6.4%) means you are at high risk of type 2 diabetes, often described as prediabetes or non-diabetic hyperglycaemia. Under the American Diabetes Association, prediabetes begins at 5.7%, so 6.0% and 6.1% are well inside it.

So the same number may be described as "borderline" on one report and "prediabetes" on another. What matters more is the trend and your other risk factors: weight, waist size, blood pressure, family history, ethnicity and activity levels.

HbA1c 6.0 average blood sugar

Estimated average glucose (eAG) for common HbA1c values, from a widely used formula. It includes after-meal peaks, so it sits above a typical fasting value:

5.7% (39 mmol/mol): about 6.5 mmol/L (117 mg/dL)
6.0% (42 mmol/mol): about 7.0 mmol/L (126 mg/dL)
6.5% (48 mmol/mol): about 7.8 mmol/L (140 mg/dL)
7.0% (53 mmol/mol): about 8.6 mmol/L (154 mg/dL)

When HbA1c can be misleading

HbA1c depends on red cells living a normal lifespan. It can read falsely low after blood loss, in haemolysis or during pregnancy, and falsely high in iron or B12 deficiency, when red cells live longer. Some haemoglobin variants, more common in people of African, Mediterranean or South Asian heritage, interfere with certain lab methods. Advanced kidney disease also affects it. In these cases doctors may rely on fasting glucose or a glucose tolerance test instead.

When to see a doctor

An HbA1c of 6.0% (42 mmol/mol) is usually discussed at a routine appointment and rechecked within a year, sooner if you have other risk factors. In the UK you may be offered the NHS Diabetes Prevention Programme. Contact your GP or doctor promptly, or seek urgent help, if you have:

an HbA1c of 6.5% (48 mmol/mol) or more, which needs confirmation and follow-up;
symptoms of high blood sugar: strong thirst, passing a lot of urine, weight loss, blurred vision, frequent infections;
vomiting, abdominal pain, rapid breathing or drowsiness with high sugar readings: go to A&E or the emergency room;
a raised HbA1c during pregnancy or when planning pregnancy.

Sources

Written using public information from:

NICE (National Institute for Health and Care Excellence): Type 2 diabetes: prevention in people at high risk (PH38)
American Diabetes Association: Standards of Care in Diabetes, diagnosis and classification
Diabetes UK: HbA1c
NHS (National Health Service, UK): Non-diabetic hyperglycaemia; NHS Diabetes Prevention Programme
World Health Organization (WHO): Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes

Upload your lab report — Ponyatno explains every value

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Frequently asked questions

Is HbA1c 6.0 normal?

Not quite. In the UK, 6.0% (42 mmol/mol) is the start of the prediabetes range. In the US it falls within prediabetes, which begins at 5.7%. It is not diabetes.

What does HbA1c 42 mmol/mol mean?

It equals 6.0% and is the lowest value of the UK prediabetes range (42 to 47 mmol/mol). It means a higher risk of type 2 diabetes in the future, which can often be reduced.

What does HbA1c 6.1 mean?

6.1% is 43 mmol/mol, inside the prediabetes range by both UK and US criteria. Your doctor will usually recheck it and look at your other risk factors.

Can prediabetes be reversed?

In many people, yes. Studies show that losing some weight if needed and being more active can return HbA1c to the normal range and lower the chance of developing type 2 diabetes. Your doctor or a prevention programme can help plan this.

How often should HbA1c be checked if it is 6.0%?

Usually once a year in the UK and US, or as your doctor advises. A rising trend matters more than a single value.

This material is for general information only. It is not a medical opinion and does not replace a consultation with a doctor. Reference ranges depend on the laboratory and the method — rely on the range printed on your own report. Your doctor makes the final interpretation.