Normal Blood Sugar Levels Guide
Quick Answer
| Test | Normal (mmol/L) | Normal (mg/dL) |
|---|---|---|
| Fasting (8 hrs no food) | 4.0 to 5.9 | 72 to 106 |
| 2 hours after eating | Below 7.8 | Below 140 |
| HbA1c (normal) | Below 39 mmol/mol | Below 5.7% |
| HbA1c (pre-diabetes) | 39 to 47 mmol/mol | 5.7 to 6.4% |
| HbA1c (diabetes) | 48 mmol/mol or above | 6.5% or above |
Unit note: the UK, Australia and most of Europe use mmol/L. The US uses mg/dL. To convert: mg/dL ÷ 18 = mmol/L.
Blood sugar (blood glucose) is one of the most important health metrics for understanding diabetes risk and managing overall metabolic health. This guide explains every threshold, unit and test clearly. For weight and calorie tools that support blood sugar management, use the BMI Calculator, Calorie Calculator and TDEE Calculator on CalConvs.
Blood Sugar Units: mmol/L vs mg/dL
- mmol/L to mg/dL: mg/dL = mmol/L × 18.0182
- mg/dL to mmol/L: mmol/L = mg/dL ÷ 18.0182
Example: 5.5 mmol/L = 5.5 × 18.0182 = 99 mg/dL. Example: 126 mg/dL = 126 ÷ 18.0182 = 7.0 mmol/L.
UK, Australia, Europe, India, Pakistan: use mmol/L. United States: uses mg/dL.
Blood Sugar Reference Ranges
| Level | mmol/L | mg/dL |
|---|---|---|
| Normal fasting | 4.0 to 5.9 | 72 to 106 |
| Normal (2 hr after meal) | Below 7.8 | Below 140 |
| Pre-diabetes fasting | 6.1 to 6.9 | 110 to 125 |
| Pre-diabetes (2 hr after meal) | 7.8 to 11.0 | 140 to 199 |
| Diabetes diagnosis fasting | 7.0 or above | 126 or above |
| Diabetes (2 hr after meal) | 11.1 or above | 200 or above |
| Hypoglycaemia (too low) | Below 4.0 | Below 72 |
| Dangerous high (emergency) | Above 33.3 | Above 600 |
What Is HbA1c?
HbA1c (glycated haemoglobin) reflects your average blood sugar over the past 2 to 3 months. Unlike a fasting glucose test, it gives a long-term picture.
| HbA1c Level | What It Means |
|---|---|
| Below 5.7% (below 39 mmol/mol) | Normal. Low risk of diabetes. |
| 5.7 to 6.4% (39 to 47 mmol/mol) | Pre-diabetes. Lifestyle intervention recommended. |
| 6.5% or above (48 mmol/mol or above) | Diabetes diagnosis (if confirmed on two occasions). |
| Target for managed diabetes | Below 7.0% (below 53 mmol/mol) for most adults. |
Blood Sugar and Diabetes by Country
- United States: Uses mg/dL. ADA guidelines widely followed. Diabetes affects approximately 11.6% of US adults.
- United Kingdom: Uses mmol/L. NICE guidelines. HbA1c is the primary diagnostic tool.
- India: Over 100 million people with diabetes, one of the highest totals globally. RSSDI guidelines.
- Pakistan: Very high diabetes prevalence, estimated 30% of adults in urban areas. Pakistan Endocrine Society guidelines.
- Australia: Uses mmol/L. RACGP guidelines. National screening programme via GP visits.
Lifestyle Factors That Affect Blood Sugar
- Diet: High refined carbohydrate and sugar intake raises post-meal glucose spikes.
- Exercise: Physical activity improves insulin sensitivity and lowers fasting glucose over time.
- Body weight: Excess body fat, particularly visceral fat, is strongly linked to insulin resistance.
- Sleep: Poor sleep raises cortisol and glucose levels.
- Stress: Chronic stress raises blood sugar through cortisol release.
- Alcohol: Can cause unpredictable blood sugar swings.
Frequently Asked Questions
What is a normal blood sugar level in the morning?
A normal fasting blood sugar before eating is 4.0 to 5.9 mmol/L (72 to 106 mg/dL). A reading of 6.0 to 6.9 mmol/L (108 to 124 mg/dL) indicates pre-diabetes. A reading of 7.0 mmol/L (126 mg/dL) or above on two separate occasions indicates diabetes.
What blood sugar level is dangerous?
A blood sugar below 4.0 mmol/L (72 mg/dL) is hypoglycaemia and can cause dizziness, confusion and loss of consciousness. Above 33.3 mmol/L (600 mg/dL) is a hyperglycaemic emergency. If either occurs, seek immediate medical attention.
Is 6.5 mmol/L blood sugar high?
A fasting blood sugar of 6.5 mmol/L is in the pre-diabetes range (6.1 to 6.9 mmol/L). It is not yet a diabetes diagnosis but is a clear signal to review diet, exercise and weight. Repeat testing is recommended.
How do I convert my US blood sugar to UK units?
Divide the US mg/dL figure by 18. For example, 108 mg/dL ÷ 18 = 6.0 mmol/L. Multiply mmol/L by 18 to convert back.
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