Fasting blood glucose reference range
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Fasting Blood Glucose Reference Range: International and Population-Specific Insights
Standard Fasting Blood Glucose Reference Range
The typical reference range for fasting blood glucose (FBG) in healthy adults is generally considered to be between 80 and 120 mg/dL (4.4–6.7 mmol/L) according to standard clinical guidelines, with values above this range indicating possible diabetes or impaired glucose regulation . However, the lower end of the normal range is often cited as 70 mg/dL (3.9 mmol/L), and the upper limit as 99 mg/dL (5.5 mmol/L), with impaired fasting glucose (IFG) defined as 100–125 mg/dL (5.6–6.9 mmol/L) Shaw2000Tirosh2005.
Population-Specific Reference Ranges
Sudanese Adults
A study in Sudanese healthy adults found that the mean FBG was 74.3 ± 13.8 mg/dL, with a reference range of 60.5 to 88.1 mg/dL. This is notably lower than international reference values, suggesting that local populations may have different normal ranges and that using Western reference intervals may not be appropriate for all populations .
Indian Adults (Kerala)
In a healthy adult population from Kerala, India, the mean fasting blood glucose was 80.97 ± 10.11 mg/dL. The study found no significant difference between males and females, but older age groups (50–59 years) had slightly higher mean values. This supports the idea that age and ethnicity can influence reference intervals .
Chinese Longevity Population
Among Chinese individuals aged 90 years and above, desirable fasting plasma glucose was defined as less than 6.15 mmol/L (110.7 mg/dL), with borderline and high levels set at 6.15–7.45 mmol/L (110.7–134.1 mg/dL) and ≥7.45 mmol/L (≥134.1 mg/dL), respectively. These values were higher than those found in younger populations, indicating that reference intervals may shift with age .
Fasting Blood Glucose and Diabetes Risk
Research shows that even within the normal range, higher fasting plasma glucose levels are associated with an increased risk of developing type 2 diabetes. For example, young men with fasting glucose levels of 87 mg/dL (4.83 mmol/L) or more had a higher risk of future diabetes compared to those with lower levels . Similarly, cardiovascular risk and risk of future diabetes increase continuously with rising FBG, with no clear threshold, suggesting that even small increases within the normal range can be clinically significant .
Fasting Blood Glucose Targets in Diabetes Management
For patients with type 2 diabetes, studies in Chinese populations suggest that an optimal FBG target is ≤6.1 mmol/L (110 mg/dL) to achieve good glycemic control (HbA1c <7.0%) without excessive risk of hypoglycemia. A stricter target of ≤5.6 mmol/L (101 mg/dL) may be suitable for those at low risk of hypoglycemia Yang2019Yang2019. In older adults with diabetes, the optimal FBG range may vary depending on other risk factors and comorbidities .
Animal Models
In laboratory mice (Mus musculus), the reference range for fasting blood glucose was found to be 72–105 mg/dL, with no significant difference between males and females. This information is useful for research but not directly applicable to humans .
Conclusion
The reference range for fasting blood glucose in healthy adults is generally 70–99 mg/dL (3.9–5.5 mmol/L), but this can vary by population, age, and ethnicity. Local studies show that some populations, such as Sudanese adults, may have lower normal ranges, while older adults may have higher acceptable values. Even within the normal range, higher fasting glucose is linked to increased risk of diabetes and cardiovascular disease. For diabetes management, an FBG target of ≤6.1 mmol/L (110 mg/dL) is often optimal, but individualization is important. These findings highlight the need for population-specific reference intervals and careful interpretation of fasting blood glucose results.
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