Blood Glucose Conversion and Reference Values
Conversion and Interpretation
- To convert blood glucose from mg/dL to mmol/L, divide the mg/dL value by 18, as recommended by the American Diabetes Association 1, 2
- Example: 126 mg/dL ÷ 18 = 7.0 mmol/L, demonstrating the conversion formula 2
- Example: 180 mg/dL ÷ 18 = 10.0 mmol/L, further illustrating the conversion process 3
- The American Academy of Family Physicians suggests that impaired fasting glucose (IFG) is indicated by 100-125 mg/dL (5.6-6.9 mmol/L) 4, 5
- The American Diabetes Association states that diabetes diagnosis threshold (fasting) is ≥126 mg/dL (≥7.0 mmol/L) 4, 6
- The American Diabetes Association also indicates that diabetes diagnosis threshold (2-hour OGTT) is ≥200 mg/dL (≥11.1 mmol/L) 4, 6
Reference Values and Critical Levels
- Hypoglycemia alert is defined as <70 mg/dL (<3.9 mmol/L) by the American Diabetes Association 7
- Severe hypoglycemia is indicated by <40 mg/dL (<2.2 mmol/L) according to the Society of Critical Care Medicine 8
- Hyperglycemia requiring attention is >250 mg/dL (>13.9 mmol/L) as stated by the American Diabetes Association 7
- Severe hyperglycemia is defined as >300 mg/dL (>16.7 mmol/L) by the American Diabetes Association 7
Conversion Table
| mg/dL | mmol/L |
|---|---|
| 70 | 3.9 |
| 100 | 5.6 |
| 126 | 7.0 |
| 140 | 7.8 |
| 180 | 10.0 |
| 200 | 11.1 |
| 250 | 13.9 |
| 300 | 16.7 |
International Considerations and Pitfalls
- When reviewing international research, it is crucial to note the unit being used, as different countries prefer different units, as highlighted by the European Society of Cardiology 2, 6
- The American Diabetes Association notes that North America typically uses mg/dL, while most other countries use mmol/L 1
- Accurate interpretation of glucose values in research requires checking which unit is being reported, as emphasized by the Society of Critical Care Medicine 3, 8
- Confusing the conversion factors (multiplying by 18 instead of dividing) is a common pitfall, as warned by the American Diabetes Association 1
- Misinterpreting threshold values when reading international literature is another pitfall, as cautioned by the American Diabetes Association 6
- Failing to note which unit is being used when interpreting test results is a critical mistake, as pointed out by the American Academy of Family Physicians 4
- Not recognizing that different sample types (plasma vs. whole blood) may have different reference ranges even in the same units is an important consideration, as noted by the European Society of Cardiology 2