Most blood sugar charts you'll find online default to US units (mg/dL). In the UK, blood glucose is measured in millimoles per litre (mmol/L) instead. Here's the mmol/L-first version, based on the general guidance commonly published by the NHS and Diabetes UK.
A quick note on units
To convert between the two: mmol/L × 18 ≈ mg/dL (and mg/dL ÷ 18 ≈ mmol/L). So 5.6 mmol/L is roughly 100 mg/dL. If you're comparing a UK reading to a US-sourced chart, this conversion is the first thing to check.
Blood glucose ranges for people without diabetes
- Fasting (before eating): commonly cited as 4.0–5.4 mmol/L
- 2 hours after eating: up to 7.8 mmol/L
- Impaired fasting glycaemia (a prediabetes-equivalent range): roughly 5.5–6.9 mmol/L fasting — a level flagged as a risk indicator worth monitoring, not a diabetes diagnosis on its own
Target ranges commonly used for people with diabetes
These are general targets sometimes cited by UK diabetes guidance — always confirm your own personal target with your GP or diabetes team, since it's set individually:
- Before meals: often cited around 4–7 mmol/L
- 2 hours after meals: under 9 mmol/L for type 1 diabetes; under 8.5 mmol/L for type 2 diabetes, as commonly cited
Compare this with the US-unit ADA targets in our Healthy Blood Sugar Range for Type 2 Diabetes article — the underlying principle (a wider, safer range than "normal," set individually) is the same on both sides of the Atlantic, even though the specific published numbers vary slightly by source and guideline.
HbA1c in the UK: percentage and mmol/mol
The UK reports HbA1c in two ways: as a percentage (the same as the US) and as mmol/mol, using the IFCC unit. As a rough guide, an HbA1c of 6.5% is approximately 48 mmol/mol, which is the commonly cited UK diagnostic threshold for diabetes. If your GP surgery gives you a result in mmol/mol, it's worth asking for the percentage equivalent too if you're used to that format.
Why UK and US numbers sometimes look slightly different
You'll notice the "normal fasting" figures above (4.0–5.4 mmol/L, roughly 72–97 mg/dL) are close to, but not perfectly identical to, the American Diabetes Association's under-100 mg/dL (5.6 mmol/L) threshold. This isn't a contradiction — different health authorities round their public-facing guidance slightly differently, and both are describing the same underlying physiology. For the full picture across both unit systems, see our complete healthy blood sugar levels guide.
Everyday habits, wherever you're based
The habits that support healthy levels don't change by country — see How to Maintain Healthy Blood Sugar Levels, or explore the GlycoBalance formula as a daily nutritional complement.
The takeaway
UK blood sugar guidance uses mmol/L rather than mg/dL, with normal fasting readings commonly cited around 4.0–5.4 mmol/L and post-meal readings under 7.8 mmol/L. If you're ever unsure which unit a number is in, check whether it's a single digit with a decimal (mmol/L) or a number in the double-or-triple digits (mg/dL) — that alone usually tells you which system you're looking at.