Prediabetes Fasting Blood Glucose: UK Guide

Prediabetes fasting blood glucose sits in a range that is higher than normal but not yet diagnostic of type 2 diabetes. In the UK, a fasting plasma glucose of 6.1 to 6.9 mmol/L indicates impaired fasting glycaemia, while the NHS Diabetes Prevention Programme accepts referrals from 5.5 mmol/L upwards. Because prediabetes rarely causes symptoms, many people are unaware of it until a routine test flags a result. Understanding what your fasting glucose result means, how the test is done, and what steps you can take is essential for reducing your risk of progressing to type 2 diabetes.

What fasting blood glucose level means you have prediabetes?

A fasting blood glucose of 6.1 to 6.9 mmol/L indicates impaired fasting glycaemia (prediabetes) under WHO and NHS criteria; 7.0 mmol/L or above on two occasions is diagnostic of type 2 diabetes.

A fasting blood glucose level of 6.1 to 6.9 mmol/L indicates impaired fasting glycaemia (IFG), which is one form of prediabetes, according to WHO diagnostic criteria and NHS clinical guidance. A result of 7.0 mmol/L or above on two separate occasions (or once if symptoms of diabetes are present) meets the diagnostic threshold for type 2 diabetes. Prediabetes sits in the middle: blood glucose is higher than it should be, but not yet high enough to confirm a diabetes diagnosis.

It is worth knowing that UK referral programmes use a slightly broader range. The NHS Diabetes Prevention Programme (NHS DPP) accepts referrals for people with a fasting plasma glucose of 5.^[1][10]5 to 6.9 mmol/L, so a result between 5.5 and 6.0 mmol/L is not simply "normal" in a programme context: it is considered high risk and may warrant lifestyle support. The WHO defines IFG as 6.1 to 6.9 mmol/L, and this is the threshold used for a clinical diagnosis of impaired fasting glycaemia.

Non-diabetic hyperglycaemia can also be identified using HbA1c. An HbA1c of 42 to 47 mmol/mol indicates non-diabetic hyperglycaemia; 48 mmol/mol or above on two occasions is diagnostic of type 2 diabetes (or once if symptoms are present).^[1][3]

The term "prediabetes" covers two overlapping conditions: IFG (identified by fasting glucose) and impaired glucose tolerance (IGT), which is identified through an oral glucose tolerance test (OGTT). IGT is defined as a two-hour glucose of 7.8 to 11.0 mmol/L during an OGTT; a two-hour result of 11.1 mmol/L or above indicates diabetes. Some people have both IFG and IGT. NICE guidance (PH38) recommends that people identified with non-diabetic hyperglycaemia are offered structured lifestyle support, because the condition is associated with a meaningfully elevated risk of progressing to type 2 diabetes.

Diagnostic cut-offs are nationally standardised, though laboratory assays may differ slightly between sites; your result should always be interpreted by a clinician in the context of your full clinical picture. Repeat testing is standard practice before any formal diagnosis is made unless symptoms are present. If you have received a result in this range, your GP is the right first point of contact for interpretation and next steps.

How is a fasting blood glucose test carried out on the NHS?

An NHS fasting blood glucose test requires eight to ten hours of fasting beforehand; blood is taken at a GP surgery or phlebotomy service, with results typically returned within a few days.

A fasting blood glucose test on the NHS is a straightforward blood test that requires you to avoid eating or drinking anything other than water for at least eight to ten hours beforehand, typically overnight. You should continue taking any prescribed medicines unless your GP or nurse specifically advises otherwise. The test is usually arranged by your GP or practice nurse, and the blood sample is taken from a vein in your arm at the surgery or at a local NHS phlebotomy service. Results are generally returned within a few days and reviewed by your GP.

The test is commonly requested as part of a routine NHS Health Check, which is offered to adults aged 40 to 74 in England who do not already have a known condition such as diabetes or cardiovascular disease. It may also be requested if you have symptoms suggestive of raised blood glucose, or if a previous result was borderline. In some cases, a GP may request an HbA1c test alongside or instead of a fasting glucose test; HbA1c reflects average blood glucose over the preceding two to three months and does not require fasting. However, HbA1c is not suitable for diagnosing gestational diabetes, and may be unreliable in people with certain haemoglobinopathies, haemolytic anaemia, or advanced chronic kidney disease; in these situations, fasting glucose or an OGTT is preferred.^[11]

If your fasting glucose result falls in the prediabetes range, your GP may arrange a repeat test or an oral glucose tolerance test (OGTT) to clarify the picture. The OGTT involves a fasting blood draw, followed by a glucose drink, and a second blood draw two hours later. This gives a more detailed view of how your body handles glucose and can identify impaired glucose tolerance that a fasting test alone might miss. Your GP surgery will give you specific preparation instructions before any of these tests.

What symptoms and risk factors are linked to raised fasting glucose?

Raised fasting glucose often causes no symptoms; key risk factors include overweight, family history of type 2 diabetes, South Asian or Black ethnicity, age over 40, gestational diabetes, and physical inactivity.

Raised fasting blood glucose often causes no noticeable symptoms at all, which is why prediabetes frequently goes undetected without routine testing. When symptoms do occur, they can include increased thirst, passing urine more often than usual, unexplained fatigue, and blurred vision. However, these symptoms are more commonly associated with established type 2 diabetes than with prediabetes, and many people in the prediabetes range feel entirely well.

If a child, young person, or young adult develops rapid-onset thirst, frequent urination, and unexplained weight loss, this warrants same-day clinical assessment to exclude type 1 diabetes, which has a different cause and management pathway.

Several risk factors are associated with impaired fasting glycaemia and a higher likelihood of progressing to type 2 diabetes. These include:

• Being overweight or living with obesity, particularly where excess weight is carried around the abdomen

• A family history of type 2 diabetes in a first-degree relative

• Ethnicity: people of South Asian, Black African, Black Caribbean, or Chinese heritage have a higher risk at a lower body mass index^[1][16]

• Age: risk increases from around 40 years, though younger adults with other risk factors are also affected

• A history of gestational diabetes during pregnancy

• Polycystic ovary syndrome (PCOS)

• Physical inactivity and a sedentary lifestyle

• High blood pressure or raised cholesterol, which often cluster with impaired glucose regulation

• Long-term use of certain medicines, including corticosteroids and some antipsychotics, which can raise blood glucose

• Obstructive sleep apnoea, which is associated with insulin resistance^[13]

The NHS Health Check programme is specifically designed to identify people with these risk factors before symptoms develop. If you have one or more of the above, it is worth discussing routine glucose testing with your GP, even if you feel well. Early identification gives the greatest opportunity to make changes that can prevent or delay progression to type 2 diabetes.

Can you bring your fasting blood glucose back to a normal range?

Yes, sustained lifestyle changes including reduced refined carbohydrate intake, increased physical activity, and clinically meaningful weight loss can return fasting glucose to the normal range.

Yes, it is possible to bring a raised fasting blood glucose back into the normal range through sustained lifestyle changes, and this is supported by robust evidence. NICE guideline PH38 (Type 2 diabetes: prevention in people at high risk) recommends that adults with non-diabetic hyperglycaemia are referred to an intensive lifestyle programme, such as the NHS Diabetes Prevention Programme (NHS DPP), which is available in England and offers group-based support over several months. The NHS DPP accepts referrals for people with a fasting plasma glucose of 5.^[1][10]5 to 6.9 mmol/L or an HbA1c of 42 to 47 mmol/mol.

The dietary changes most consistently associated with improved glucose regulation include reducing intake of refined carbohydrates and added sugars, increasing dietary fibre, and following an overall eating pattern that supports a healthy body weight. Aerobic exercise, such as brisk walking, cycling, or swimming, improves insulin sensitivity and can lower fasting glucose independently of weight loss. UK Chief Medical Officers' guidelines recommend at least 150 minutes of moderate-intensity activity per week for adults.^[7][8]

For people with a higher body mass index, clinically meaningful weight loss (broadly in the region of 5 to 10 per cent of body weight) has been shown to significantly reduce the risk of progression to type 2 diabetes.^[12][1] NICE PH38 also notes that metformin may be considered for selected high-risk adults in whom lifestyle measures are insufficient or cannot be implemented, though medicines are not routinely used to treat prediabetes in the UK.^[1][2] Any decision about pharmacological support should be made with your GP following individual assessment. Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support; a prescriber may consider a range of clinically appropriate options following assessment.

It is important to have your blood glucose monitored regularly after a prediabetes result, even if you feel your lifestyle has improved, as some people do progress despite making changes.

When should you see a GP about your blood glucose results?

See your GP if your fasting glucose is 6.1 mmol/L or above, if you have symptoms of raised blood glucose, or if a result of 7.0 mmol/L or above is returned, as this may indicate type 2 diabetes.

You should see your GP if you receive a fasting blood glucose result of 6.1 mmol/L or above, if you have symptoms that could suggest raised blood glucose, or if you have multiple risk factors for type 2 diabetes and have not been tested recently. A result in the prediabetes range (6.1 to 6.9 mmol/L) warrants a follow-up appointment to discuss what the result means, whether repeat testing is needed, and what lifestyle support is available to you. If you have a fasting glucose of 5.5 to 6.0 mmol/L and other risk factors, it is also worth discussing this with your GP, as you may be eligible for the NHS Diabetes Prevention Programme.

Contact your GP promptly, rather than waiting for a routine review, if you experience any of the following:

• Persistent or worsening thirst and frequent urination, particularly at night

• Unexplained weight loss alongside fatigue

• Recurrent infections, such as thrush or urinary tract infections, which can be associated with elevated blood glucose

• A fasting glucose result of 7.0 mmol/L or above, which may indicate type 2 diabetes and requires prompt clinical assessment; in symptomatic individuals, a single result at this level may be sufficient for diagnosis

If a child or young person develops rapid-onset symptoms of high blood glucose, seek same-day assessment. If you feel acutely unwell, are confused, or are vomiting and unable to keep fluids down alongside symptoms of high blood glucose, seek urgent help via NHS 111 or, if you are seriously unwell, attend your nearest accident and emergency department.

For ongoing monitoring, NICE PH38 recommends that people with confirmed non-diabetic hyperglycaemia have their HbA1c or fasting glucose checked at least annually.^[1][2] This allows your GP to track whether your glucose levels are stable, improving, or progressing. Keeping a record of your results over time, and attending any structured lifestyle programme you are referred to, will help you and your GP make informed decisions about your care. Suspected adverse effects from any medicines you are taking can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

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) – Guidance overview.
3. Preventing the progression of pre-diabetes to type 2 diabetes – Evidence review R1: identification and risk assessment of adults with prediabetes.
4. Diabetes.
5. NHS Health Check.
6. First national evaluation of NHS Health Check programme published.
7. Physical activity guidelines: UK Chief Medical Officers' report.
8. UK Chief Medical Officers' physical activity guidelines – guidance document.
9. Physical activity guidelines for adults aged 19 to 64.
10. Referring people at high risk of type 2 diabetes (QS167, Quality statement 3).
11. Diabetes in pregnancy: management from preconception to the postnatal period (NG3) – Recommendations.
12. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. Knowler WC et al. N Engl J Med..
13. Obstructive sleep apnoea and type 2 diabetes mellitus. Aurora RN et al. Lancet Respir Med..
14. Diabetes: NDH annual HbA1c or FPG test (IND172).
15. NM150 guidance document – Annual HbA1c testing in non-diabetic hyperglycaemia.
16. Health matters: preventing type 2 diabetes.

Frequently Asked Questions