Normal fasting blood glucose levels
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Normal Fasting Blood Glucose Levels: Definitions and Ranges
Normal fasting blood glucose (FBG) levels are generally defined as less than 100 mg/dL (5.55 mmol/L) 12346. Some sources specify the normal range as between 80 and 120 mg/dL, with most clinical guidelines recommending a fasting blood sugar between 80 and 130 mg/dL as the target for healthy individuals 56.
Risk of Diabetes Within the Normal Fasting Glucose Range
Research shows that even within the normal range, higher fasting glucose levels are linked to an increased risk of developing type 2 diabetes. Individuals with fasting glucose levels at the higher end of the normal range (91–99 mg/dL) have a significantly greater risk of progressing to diabetes compared to those with lower normal levels (<85 mg/dL) 1234. The risk increases progressively with each milligram per deciliter rise in fasting glucose, even after accounting for other risk factors like age, body mass index, and triglyceride levels 1234.
Cardiovascular Risk and High-Normal Fasting Glucose
Higher fasting glucose levels within the normal range are also associated with an increased risk of cardiovascular disease (CVD). People with fasting glucose levels of 95–99 mg/dL have a higher risk of CVD compared to those with levels below 80 mg/dL, even if they do not have diabetes 49. This suggests that monitoring fasting glucose, even within the normal range, can help identify individuals at risk for both diabetes and cardiovascular problems.
Fasting Glucose in Special Populations
In obese youth, higher normal fasting glucose levels are linked to reduced insulin sensitivity and beta cell function, which are early signs of metabolic problems . This means that even children and adolescents with high-normal fasting glucose may benefit from closer monitoring and early lifestyle interventions.
Limitations of Fasting Glucose for Diabetes Diagnosis
Relying solely on fasting glucose for diabetes screening can miss early or post-meal (postprandial) cases of diabetes, as a significant number of people with normal fasting glucose may still develop diabetes based on other criteria . Therefore, both the absolute value and changes in fasting glucose over time should be considered for better prevention and early detection.
Conclusion
Normal fasting blood glucose levels are typically less than 100 mg/dL, with optimal targets often cited as 80–130 mg/dL. However, higher values within this range (especially 91–99 mg/dL) are associated with increased risks for type 2 diabetes and cardiovascular disease. Regular monitoring and attention to trends in fasting glucose, even within the normal range, are important for early identification of individuals at risk and for guiding preventive health measures.
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