Blood Glucose of 120: What It Means

A blood glucose of 120 mg/dL (approximately 6.7 mmol/L) is a reading many people encounter and are unsure how to interpret. In the UK, blood glucose is reported in mmol/L, so understanding what this figure means in a UK clinical context is important. Sitting above the normal fasting range but below the diagnostic threshold for type 2 diabetes, a reading of 120 mg/dL may indicate impaired fasting glucose, also known as prediabetes. This article explains what the reading means, what causes it, how to bring it down, and when to seek advice from your GP.

What does a blood glucose reading of 120 actually mean?

A reading of 120 mg/dL equals approximately 6.7 mmol/L, placing it in the impaired fasting glucose range under WHO and NHS criteria, above normal but below the 7.0 mmol/L threshold for a diabetes diagnosis.

A blood glucose reading of 120 mg/dL is equivalent to approximately 6.7 mmol/L and sits above the normal fasting range but below the threshold typically used to diagnose type 2 diabetes. In the UK, blood glucose is almost always measured and reported in millimoles per litre (mmol/L), so if you have seen the figure 120, it is likely from a device calibrated in mg/dL, which is the standard unit used in the United States and some other countries.

To put this in context, NHS guidance considers a normal fasting blood glucose to be below 6.0 mmol/L (108 mg/dL). A fasting reading between 6.1 and 6.9 mmol/L (roughly 110 to 124 mg/dL) is classified as impaired fasting glucose (sometimes called prediabetes or non-diabetic hyperglycaemia) according to WHO diagnostic criteria, which are used in UK clinical practice. A fasting plasma glucose of 7.0 mmol/L (126 mg/dL) or above, confirmed on two separate occasions by a laboratory venous plasma test, is one of the diagnostic criteria for type 2 diabetes per NICE guidance (NG28).

It is important to note that diagnosis of diabetes or prediabetes must be based on laboratory blood tests, such as a fasting plasma glucose or an HbA1c, not on readings from a home glucose meter or continuous glucose monitor. HbA1c reflects average blood glucose over the preceding two to three months: a result of 48 mmol/mol or above on two occasions indicates diabetes, while a result of 42 to 47 mmol/mol suggests non-diabetic hyperglycaemia (the HbA1c equivalent of prediabetes), according to NHS and NICE guidance.^[1][2]

The meaning of any single reading also depends heavily on when it was taken. A blood glucose of 6.7 mmol/L measured two hours after a meal may be within an acceptable postprandial range (NHS and Diabetes UK guidance suggests below 7.8 mmol/L at two hours after eating for people without diabetes), whereas the same figure taken after an overnight fast would warrant further investigation. A single reading should never be used in isolation to make or dismiss a diagnosis; your GP will consider the timing, your symptoms, and a confirmatory laboratory test.

Is 120 mg/dL (or 6.7 mmol/L) too high for me?

Whether 6.7 mmol/L is too high depends on timing, your health profile, and any existing diabetes diagnosis; for most adults without diabetes, a fasting reading at this level falls within the impaired fasting glucose range and warrants further assessment.

Whether 6.7 mmol/L is too high depends on the context of the measurement, your individual health profile, and whether you already have a diagnosis of diabetes. For most adults without diabetes, a fasting reading of 6.7 mmol/L falls within the impaired fasting glucose range, which NICE and the NHS recognise as a risk factor for developing type 2 diabetes. It is not a normal result, but it is not a diabetes diagnosis either.

For people who are already living with type 2 diabetes, target blood glucose ranges are set individually. NHS and Diabetes UK guidance suggests that for adults with type 2 diabetes, a pre-meal (fasting) capillary blood glucose target of 4.0 to 7.0 mmol/L is generally appropriate for many people, though individual targets are agreed with a GP or diabetes care team. NICE (NG28) primarily frames glycaemic targets in terms of HbA1c (for example, 48 mmol/mol where appropriate, or up to 53 mmol/mol in certain circumstances), and your care team will use both measures together. A reading of 6.7 mmol/L before a meal would sit at the upper end of the commonly used pre-meal range but would not necessarily be considered dangerously elevated.

For people with type 1 diabetes, targets may differ and are agreed with a specialist diabetes team. Pregnant women have tighter glucose targets: NICE guidance (NG3, Diabetes in pregnancy) advises a fasting target below 5.3 mmol/L, and a reading of 6.7 mmol/L fasting would be above this threshold.

Age, kidney function, cardiovascular history, and the risk of hypoglycaemia all influence what target is appropriate for a given individual. This is why a personalised conversation with your GP or diabetes care team is essential rather than relying on a single number in isolation.

What causes blood sugar to sit around 120?

Persistent fasting glucose around 6.7 mmol/L is most commonly caused by insulin resistance or reduced insulin secretion, often linked to excess body weight, physical inactivity, poor sleep, stress, or certain medicines such as corticosteroids.

Blood glucose sitting persistently around 6.7 mmol/L (120 mg/dL) in a fasting state is most commonly caused by insulin resistance, reduced insulin secretion, or a combination of both. These are the underlying mechanisms in prediabetes and type 2 diabetes, where the body either does not produce enough insulin or does not respond to it effectively, resulting in glucose remaining in the bloodstream rather than being taken up by cells.

Several lifestyle and physiological factors can contribute to elevated fasting glucose:

• Diet: A diet high in refined carbohydrates, sugary drinks, and ultra-processed foods raises postprandial glucose and, over time, can impair fasting levels.

• Physical inactivity: Skeletal muscle is a major site of glucose uptake; reduced activity lowers insulin sensitivity.

• Excess body weight: Particularly central (abdominal) adiposity is strongly associated with insulin resistance.

• Poor sleep: Short or disrupted sleep raises cortisol and growth hormone levels, both of which increase blood glucose.

• Stress: Chronic psychological stress elevates cortisol, which stimulates hepatic glucose production.

• Certain medicines: Corticosteroids, some antipsychotics, and thiazide diuretics can raise blood glucose as a recognised side effect; this is documented in NHS and BNF guidance for these drug classes.^[8]

• Other medical conditions: Polycystic ovary syndrome (PCOS), metabolic dysfunction-associated steatotic liver disease (MASLD, previously known as non-alcoholic fatty liver disease or NAFLD), and some hormonal disorders such as Cushing's syndrome or acromegaly can all contribute.

In some cases, a reading around 6.7 mmol/L may reflect normal postprandial variation rather than a persistent problem, particularly if the measurement was taken within two hours of eating. Keeping a log of readings alongside meal times helps your GP interpret the pattern accurately.

How can I bring my blood glucose down to a healthy range?

Structured lifestyle changes, including reducing refined carbohydrates, increasing physical activity, and managing weight, are the NICE-recommended first-line approach; the free NHS Diabetes Prevention Programme supports people at high risk.

Bringing blood glucose down from around 6.7 mmol/L to a healthier fasting range is achievable for many people through structured lifestyle changes, and NICE guidance strongly supports this approach as the first-line intervention for impaired fasting glucose and early type 2 diabetes. The NHS Diabetes Prevention Programme (NHS DPP, also known as NHS Healthier You) offers a free, evidence-based structured education programme for adults in England identified as being at high risk, and referral is available through your GP.

Key lifestyle strategies include:

• Dietary adjustment: Reducing refined carbohydrates and added sugars, increasing fibre intake from vegetables, pulses, and wholegrains, and moderating portion sizes can meaningfully lower fasting glucose. A Mediterranean-style or low-glycaemic-index diet has good evidence behind it, as recognised in Diabetes UK nutrition guidance.

• Regular physical activity: The UK Chief Medical Officers' Physical Activity Guidelines recommend at least 150 minutes of moderate-intensity aerobic activity per week, alongside muscle-strengthening activity on two or more days.^[9][10] Even a 10 to 15 minute walk after meals can help reduce postprandial glucose rises, a finding supported by published research in people with impaired glucose regulation.^[12]

• Weight management: Losing 5 to 10 per cent of body weight in people who are overweight has been shown to significantly improve insulin sensitivity and reduce fasting glucose.^[16] For some people with type 2 diabetes, greater weight loss can lead to remission, as demonstrated by the DiRECT trial and supported by Diabetes UK remission resources.^[13]

• Sleep and stress: Addressing poor sleep hygiene and chronic stress through behavioural strategies or appropriate support can have a measurable effect on glucose regulation.

If lifestyle changes alone are insufficient, your GP may consider medication. Metformin is the most commonly prescribed first-line agent for type 2 diabetes in the UK, as recommended by NICE (NG28). For people with obesity and type 2 diabetes or those requiring additional weight management support, other MHRA-authorised medicines may be considered. Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, where clinically appropriate options may be discussed.

Any medication decision should be made in partnership with a qualified prescriber who has access to your full medical history.

When should I speak to my GP about my blood sugar levels?

Speak to your GP if fasting readings of 6.0 mmol/L or above occur on more than one occasion, or promptly if you develop symptoms such as increased thirst, frequent urination, fatigue, or slow-healing wounds.

You should speak to your GP if you have a fasting blood glucose reading of 6.0 mmol/L or above on more than one occasion, as this falls outside the normal range and warrants formal assessment in line with NHS guidance on diagnosing diabetes. A single elevated reading does not confirm a diagnosis, but it is a clear signal that further investigation is needed. Your GP may arrange a repeat fasting plasma glucose, an HbA1c blood test (which reflects average blood glucose over the preceding two to three months), or in certain circumstances an oral glucose tolerance test (OGTT), for example during pregnancy or in borderline cases.^[6]

If you are pregnant and concerned about your blood glucose readings, raise this promptly with your midwife or antenatal diabetes team rather than waiting for a routine GP appointment, as tighter monitoring and earlier assessment are recommended during pregnancy (NICE NG3).

Contact your GP promptly if you notice any of the following alongside elevated readings:

• Increased thirst or a dry mouth that does not resolve

• Passing urine more frequently than usual, particularly at night

• Unexplained fatigue or lack of energy

• Blurred vision

• Slow-healing cuts or wounds

• Recurrent infections, such as thrush or urinary tract infections

• Unintentional weight loss

These symptoms may indicate that blood glucose has been elevated for some time and that a formal diabetes assessment is needed without delay. Your GP can arrange the appropriate blood tests and, if a diagnosis is confirmed, refer you to a structured diabetes education programme and specialist support where required.

If you are already diagnosed with diabetes and experience symptoms of very high blood glucose (hyperglycaemia) such as vomiting, confusion, or rapid breathing, contact NHS 111 for urgent advice or attend your nearest accident and emergency department if you feel seriously unwell. For routine concerns about your readings or medication, your GP or diabetes nurse is the right first point of contact.

Healthcare professionals and patients can report suspected adverse reactions to medicines to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Scientific References

1. High blood sugar (hyperglycaemia).
2. Type 2 diabetes in adults: management (NG28).
3. Blood glucose management | Type 2 diabetes in adults (NG28).
4. Initial medicines | Type 2 diabetes in adults: management (NG28).
5. Diabetes in pregnancy: management from preconception to the postnatal period (NG3).
6. HbA1c | Information for the public | Type 1 diabetes in adults (NG17).
7. Type 2 diabetes | Treatment summaries - BNF - NICE.
8. Corticosteroids, general use | Treatment summaries - BNF - NICE.
9. Physical activity guidelines: UK Chief Medical Officers' report.
10. UK Chief Medical Officers' physical activity guidelines - GOV.UK.
11. Physical activity guidelines for adults aged 19 to 64 - NHS.
12. After Dinner Rest a While, After Supper Walk a Mile? A Systematic Review with Meta-analysis on the Acute Postprandial Glycemic Response to Exercise Before and After Meal Ingestion in Healthy Subjects and Patients with Impaired Glucose Tolerance.
13. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial.
14. Low blood sugar (hypoglycaemia).
15. Health matters: preventing Type 2 Diabetes - GOV.UK.
16. Overweight and obesity in adults - NHS.

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