From the Guidelines
A normal fasting blood glucose level is less than 100 mg/dL (5.6 mmol/L), as defined by recent guidelines. This measurement is taken after not eating or drinking anything except water for at least 8 hours. Values between 100 and 125 mg/dL (5.6 to 6.9 mmol/L) indicate prediabetes, while a fasting blood glucose of 126 mg/dL (7.0 mmol/L) or higher on two separate tests suggests diabetes 1. For accurate results, follow your healthcare provider's instructions about fasting completely before the test. Blood glucose levels naturally fluctuate throughout the day in response to food intake, physical activity, stress, and other factors. The fasting measurement is particularly valuable because it shows your baseline glucose level when digestive processes aren't actively affecting blood sugar. This helps healthcare providers assess how well your body regulates glucose when not processing food, which is important for diagnosing diabetes and monitoring overall metabolic health.
Key Points to Consider
- Normal fasting glucose is defined as glucose <100 mg/dL (5.6 mmol/L) 1
- Impaired fasting glucose has been defined as a fasting plasma glucose of 100 mg/dL to 125 mg/dL (5.6 mmol/L to 6.9 mmol/L) 1
- A fasting plasma glucose level ≥126 mg/dL (7.0 mmol/L), or A1C ≥6.5%, or a casual plasma glucose >200 mg/dL (11.1 mmol/L) in the setting of symptoms attributable to hyperglycemia meets the threshold for the diagnosis of diabetes 1
- The American Diabetes Association recommends using A1C measurement as a diagnostic and screening tool for diabetes, with an A1C level of greater than 6.5 percent on two separate occasions considered diagnostic of diabetes 1
Importance of Accurate Diagnosis
Accurate diagnosis of diabetes and prediabetes is crucial for early intervention and prevention of complications. Healthcare providers should use the most recent guidelines and evidence-based recommendations to diagnose and manage diabetes, taking into account individual patient factors and risk profiles 1. By prioritizing accurate diagnosis and effective management, healthcare providers can help improve patient outcomes and reduce the risk of morbidity and mortality associated with diabetes.
From the Research
Normal Fasting Blood Glucose Levels
- A normal fasting blood glucose level is typically defined as less than 100 mg per deciliter (5.55 mmol per liter) 2.
- However, some studies suggest that higher fasting plasma glucose levels within the normoglycemic range may constitute an independent risk factor for type 2 diabetes among young men 2.
- Impaired fasting glucose is defined as glucose levels of 100 to 125 mg per dL (5.6 to 6.9 mmol per L) in fasting patients, which is above normal but below the level that is diagnostic for diabetes 3.
- The American Diabetes Association defines normal fasting plasma glucose as less than 100 mg/dL, impaired fasting glucose as 100-125 mg/dL, and diabetes as 126 mg/dL or higher 4.
Risk Factors and Associations
- Risk factors for diabetes include family history of diabetes, body mass index greater than 25 kg per m2, sedentary lifestyle, hypertension, dyslipidemia, history of gestational diabetes or large-for-gestational-age infant, and polycystic ovary syndrome 3.
- Impaired fasting glucose is associated with an increased risk of cardiovascular disease mortality, particularly in the presence of moderate systolic hypertension 5.
- Metformin has been shown to reduce fasting blood glucose and insulin concentrations, and may be useful in preventing the progression to glucose intolerance in high-risk patients, such as obese adolescents with a family history of type 2 diabetes 6.