Prediabetes Range UK: HbA1c and Glucose Levels

Understanding the prediabetes range is an important first step in protecting your long-term health. In the UK, prediabetes (known clinically as non-diabetic hyperglycaemia) is defined by an HbA1c of 42 to 47 mmol/mol or a fasting plasma glucose of 6.1 to 6.9 mmol/L, sitting above normal but below the threshold for type 2 diabetes. Because prediabetes rarely causes noticeable symptoms, many people are unaware they are affected until a routine blood test reveals an elevated result. The good news is that with the right lifestyle changes, blood glucose can return to the normal range.

What blood sugar levels count as prediabetes in the UK?

In the UK, prediabetes is defined as an HbA1c of 42 to 47 mmol/mol or a fasting plasma glucose of 6.1 to 6.9 mmol/L, both sitting above normal but below the type 2 diabetes diagnostic threshold.

In the UK, prediabetes (also called non-diabetic hyperglycaemia, or NDH) is most commonly identified using HbA1c or fasting plasma glucose (FPG). NHS and NICE guidance (NICE PH38) defines the HbA1c range for NDH as 42 to 47 mmol/mol (6.0% to 6.4%). For fasting plasma glucose, the World Health Organization defines impaired fasting glycaemia (IFG) as 6.1 to 6.9 mmol/L; the NHS Diabetes Prevention Programme (NHS DPP) in England uses a broader eligibility range of 5.5 to 6.9 mmol/L for programme entry. These thresholds sit above the normal range but below the diagnostic cut-off for type 2 diabetes, which begins at an HbA1c of 48 mmol/mol (6.5%) or a fasting glucose of 7.0 mmol/L or above.

It is worth understanding what these numbers represent. HbA1c reflects average blood glucose over the preceding two to three months by measuring the proportion of haemoglobin that has glucose attached to it.^[4] A fasting plasma glucose test measures the concentration of glucose in the blood after at least eight hours without eating. Both tests can be used to identify prediabetes, and the choice between them depends on clinical context and individual circumstances.

A third test, the oral glucose tolerance test (OGTT), measures blood glucose two hours after a 75 g glucose drink. An OGTT result of 7.8 to 11.0 mmol/L at two hours indicates impaired glucose tolerance (IGT), which is another form of prediabetes. The OGTT is not used routinely in primary care but is used in pregnancy and in selected clinical situations where HbA1c may be unreliable.

Neither NDH nor IGT means that progression to type 2 diabetes is inevitable. Research consistently shows that structured lifestyle intervention can return blood glucose to the normal range and substantially reduce the risk of developing type 2 diabetes.^[1][10] Understanding where your result sits within the prediabetes range is therefore a starting point for action rather than a fixed diagnosis.

How is prediabetes diagnosed on the NHS?

Prediabetes is diagnosed on the NHS primarily via an HbA1c blood test showing 42 to 47 mmol/mol; a single result in this range is generally sufficient to confirm non-diabetic hyperglycaemia.

Prediabetes is identified on the NHS primarily through a blood test measuring HbA1c, with a result of 42 to 47 mmol/mol confirming non-diabetic hyperglycaemia. A fasting plasma glucose test may also be used, particularly where HbA1c is unreliable, for example in people with certain haemoglobin variants, haemolytic anaemia, or during pregnancy.^[1][4] The WHO threshold for impaired fasting glycaemia is 6.1 to 6.9 mmol/L; the NHS DPP uses 5.5 to 6.9 mmol/L as its eligibility range.

NICE guidance (PH38) recommends that adults identified as being at high risk should have their HbA1c measured. The NHS Health Check, offered to adults aged 40 to 74 in England, is one of the most common routes through which prediabetes is identified.^[3] Adults at higher risk due to ethnicity or other factors may be assessed earlier.

A single HbA1c result in the NDH range is generally sufficient to confirm non-diabetic hyperglycaemia, unlike type 2 diabetes, where a second confirmatory test is required in the absence of symptoms. Clinicians may repeat the test after a period of lifestyle change to monitor whether glucose levels are improving, remaining stable, or progressing.

If your GP identifies a result in the prediabetes range, they should discuss the findings with you, explain what the result means, and refer you to a behaviour-change support programme where appropriate. In England, this is the NHS Diabetes Prevention Programme (NHS DPP), a free, evidence-based programme offering personalised support. Equivalent prevention programmes exist in Scotland, Wales and Northern Ireland, though delivery models and referral routes differ by nation; your GP or practice nurse can advise on local provision. You do not need to wait for symptoms before asking your GP about a blood glucose test if you have known risk factors.

What symptoms and risk factors should you know about?

Prediabetes usually causes no symptoms, so knowing your risk factors, including age over 40, elevated BMI, South Asian or Black African heritage, and family history of type 2 diabetes, is key to seeking timely testing.

Prediabetes typically causes no noticeable symptoms, which is why it is so frequently identified only through routine blood testing rather than because a person feels unwell. This absence of symptoms makes awareness of risk factors particularly important, as they help identify who should be prioritised for screening.

NICE (PH38) and NHS guidance identify the following as established risk factors for prediabetes and type 2 diabetes:

• Age: Risk increases significantly from age 40 onwards, and from age 25 in people of South Asian, Black African, or African Caribbean heritage.

• Weight: A body mass index (BMI) of 25 kg/m2 or above (or 23 kg/m2 or above in people of South Asian heritage) is associated with increased risk.^[8][9]

• Family history: Having a first-degree relative with type 2 diabetes raises risk.

• Ethnicity: People of South Asian, Black African, and African Caribbean heritage are at higher risk at lower BMI thresholds and younger ages.

• Gestational diabetes: A history of gestational diabetes increases the likelihood of developing prediabetes or type 2 diabetes later in life.

• Cardiovascular disease or hypertension: These conditions frequently co-exist with insulin resistance.

• Polycystic ovary syndrome (PCOS): Associated with insulin resistance and elevated glucose levels.

Some people with prediabetes do report increased thirst, fatigue, or needing to urinate more frequently, but these symptoms are non-specific and often attributed to other causes. If you experience any of these alongside known risk factors, contact your GP for a blood glucose assessment rather than waiting for a scheduled health check.

What lifestyle changes does the NHS recommend for prediabetes?

NICE and the NHS recommend structured lifestyle intervention, including a lower glycaemic diet, at least 150 minutes of moderate aerobic activity per week, and sustained weight loss of 5% to 10% of body weight where BMI is elevated.

NICE (PH38) and NHS guidance recommend structured lifestyle intervention as the primary approach to managing prediabetes, with evidence showing that sustained changes to diet, physical activity, and weight can return blood glucose to the normal range and significantly reduce the risk of progression to type 2 diabetes. In England, the NHS Diabetes Prevention Programme (NHS DPP) is a free, evidence-based behaviour-change programme offering personalised support; referral is typically made by a GP or practice nurse following a confirmed NDH result.

Dietary changes recommended by NHS Eatwell guidance and NICE PH38 include:

• Reducing intake of refined carbohydrates and foods with a high glycaemic index, such as white bread, sugary drinks, and processed snacks.

• Increasing fibre intake through wholegrains, vegetables, pulses, and fruit.

• Limiting saturated fat and replacing it with unsaturated sources where possible.

• Reducing overall calorie intake if weight loss is a goal.

Physical activity guidance from the UK Chief Medical Officers recommends at least 150 minutes of moderate-intensity aerobic activity per week, such as brisk walking, cycling, or swimming, alongside muscle-strengthening activities on two or more days per week.^[6][7] Even modest increases in daily movement have been shown to improve insulin sensitivity.

Weight management is particularly important where BMI is elevated. NHS DPP evidence summaries indicate that a sustained reduction of 5% to 10% of body weight is associated with meaningful improvements in blood glucose levels in people with prediabetes.^[10]

For some individuals, particularly those at high risk where lifestyle change alone has not been sufficient, a GP may consider pharmacological support. NICE PH38 notes that metformin may be considered in certain high-risk groups as an adjunct to lifestyle intervention; this is a selective clinical decision and local prescribing policies may vary.^[1][2]

Where weight management support is being explored as part of a broader clinical plan, Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support. Any prescription medicine would only be prescribed where clinically appropriate following a consultation, alongside other options your GP may discuss with you.

Regular monitoring of HbA1c, typically annually or more frequently if your risk is changing, allows your GP to track whether your blood glucose is responding to lifestyle changes or whether further assessment is needed. Your GP will advise on the interval most appropriate for your circumstances.

Scientific References

1. Type 2 diabetes: prevention in people at high risk (PH38) – Recommendations.
2. Type 2 diabetes: prevention in people at high risk (PH38) – Guideline overview.
3. NHS Health Check.
4. Diabetes.
5. Type 2 diabetes and pre-diabetes: Issues of diagnosis and definition (evidence review for PH35).
6. UK Chief Medical Officers' Physical Activity Guidelines.
7. Physical activity guidelines for adults aged 19 to 64.
8. Overweight and obesity management (NG246) – Identifying and assessing overweight, obesity and central adiposity.
9. Overweight and obesity.
10. Population level impact of the NHS Diabetes Prevention Programme.
11. Is fasting glucose sufficient to define diabetes? (PMID 10382583).

Frequently Asked Questions