Blood Sugar (HbA1c) Conversion & Tracker
Convert between HbA1c percentages, mmol/mol, and average blood glucose levels. Interpret your reading against NHS thresholds.
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HbA1c Guide
What HbA1c Measures?
HbA1c (glycated haemoglobin): the percentage of red blood cells with glucose attached. Reflects average blood glucose over the past 8-12 weeks (the lifespan of red blood cells). Unlike a finger-prick spot check, HbA1c gives a long-term picture. Why it matters: high glucose damages blood vessels, kidneys, eyes, nerves throughout the body — cumulatively. HbA1c tracks the long-term exposure that matters. NHS units: changed from % to mmol/mol in 2011 in UK. Both still in use internationally. Conversion between the two scales is straightforward using a standard formula, and most UK labs now report both figures side by side.
What's the key thing to understand about NHS Thresholds (mmol/mol)?
Below 42 (6.0%): normal, no diabetes. 42-47 (6.0-6.4%): pre-diabetes (also called impaired glucose regulation). 48+ (6.5%+): diabetes diagnosis. Targets for treated diabetes (NICE guidance): Type 2 diabetes lifestyle only: target 48 mmol/mol (6.5%). T2D on one drug not causing hypos: 48 (6.5%). T2D on insulin or sulfonylureas: 53 (7.0%) — slightly higher to balance hypoglycaemia risk. Type 1 diabetes: 48 (6.5%) if achievable without disabling hypos. Above 58 mmol/mol (7.5%): treatment intensification is usually considered, meaning your GP or diabetes team may suggest a change in medication, dose, or lifestyle approach.
What's the key thing to understand about HbA1c to Average Glucose?
Approximate conversion: average glucose (mmol/L) = (HbA1c% × 1.59) − 2.59. Or: mg/dL = (HbA1c% × 28.7) − 46.7. Examples: HbA1c 5.0% (31 mmol/mol): avg glucose 5.4 mmol/L = 97 mg/dL (normal). HbA1c 6.5% (48): avg glucose 7.8 mmol/L = 140 mg/dL (diabetes threshold). HbA1c 7.0% (53): 8.6 mmol/L = 154 mg/dL (typical T2D target). HbA1c 8.0% (64): 10.1 mmol/L = 183 mg/dL (treatment intensification needed). HbA1c 10.0% (86): 13.3 mmol/L = 240 mg/dL (poor control, complications likely). Continuous glucose monitors (CGM) give real-time readings and can help identify patterns a single HbA1c figure can't show, such as which meals or times of day cause the biggest spikes.
What should I know about Lowering HbA1c?
Lifestyle changes can dramatically reduce HbA1c: weight loss (5-10% body weight): typically 5-10 mmol/mol reduction. Carbohydrate reduction: lower starchy carb intake reduces glucose peaks. Mediterranean or low-GI diets show strong evidence. Exercise: 150 min/week moderate activity reduces HbA1c 5-7 mmol/mol on average. Strength training adds further benefit. Sleep: chronic sleep deprivation worsens insulin resistance. 7-9 hours/night supports glucose control. T2D remission: the DiRECT trial showed that substantial, sustained weight loss — around 15kg — can put type 2 diabetes into remission for many people, though this requires structured support and isn't achievable or appropriate for everyone.