Fasting blood sugar reference range
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Fasting Blood Sugar Reference Range: International and Local Variations
Standard Fasting Blood Sugar Reference Ranges
Most clinical guidelines and textbooks commonly cite a normal fasting blood sugar (FBS) range of 70–100 mg/dL (3.9–5.6 mmol/L) for healthy adults, with some sources extending the upper limit to 120 mg/dL (6.7 mmol/L) 74. However, recent research highlights that these ranges can vary based on population and methodology.
Population-Specific Reference Intervals
Studies from different regions have shown that fasting blood sugar reference ranges can differ significantly from international standards:
- In Sudan, healthy adults had a mean FBS of 74.3 mg/dL, with a reference range of 60.5–88.1 mg/dL, which is notably lower than international parameters .
- In Port Harcourt, Nigeria, the reference interval for fasting plasma glucose was found to be 3.1–5.8 mmol/L (56–104 mg/dL), which is lower than the manufacturer-provided range of 4.2–6.4 mmol/L (76–115 mg/dL) .
- In Kerala, India, the mean fasting blood glucose was 80.97 mg/dL, with age-related increases but no significant difference between males and females .
These findings emphasize the importance of establishing local reference intervals for accurate diagnosis and management.
Age and Gender Differences
Research indicates that fasting blood sugar levels can increase with age, but there is generally no significant difference between males and females in healthy populations . This suggests that age-specific reference intervals may be more relevant than gender-specific ones in some populations.
Fasting Blood Sugar and Risk of Diabetes
Even within the normal range, higher fasting blood sugar levels are associated with an increased risk of developing type 2 diabetes. For example, men with fasting plasma glucose levels of 87 mg/dL (4.83 mmol/L) or higher had a greater risk of future diabetes compared to those with lower levels . The risk increases further when combined with other factors like high triglycerides or higher body mass index .
Clinical Implications and Recommendations
- The optimal fasting blood glucose target for most patients with type 2 diabetes is ≤6.1 mmol/L (110 mg/dL), with stricter targets (≤5.6 mmol/L or 101 mg/dL) considered for those at lower risk of hypoglycemia 68.
- There is no clear threshold for defining impaired fasting glucose; risk of diabetes and cardiovascular disease increases continuously with rising fasting glucose, even below traditional cutoffs .
- Local reference intervals should be used where available, as reliance on international or manufacturer-provided ranges may not reflect the true normal values for specific populations 123.
Conclusion
The reference range for fasting blood sugar varies by population, with many local studies finding lower normal values than international standards. Age can influence fasting blood sugar, but gender differences are minimal. Higher fasting blood sugar within the normal range still increases the risk of diabetes, highlighting the need for individualized assessment and the use of locally established reference intervals for accurate clinical decision-making 12347910.
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