What are the normal values for glucose measurement?

Normal Blood Glucose Values

Normal fasting plasma glucose is less than 100 mg/dL (5.6 mmol/L), while normal post-meal glucose should be less than 140 mg/dL (7.8 mmol/L) at 2 hours after a meal. 1

Classification of Blood Glucose Levels

Blood glucose measurements are categorized into three main classifications:

Fasting Plasma Glucose (FPG)

• Normal: <100 mg/dL (<5.6 mmol/L)
• Impaired Fasting Glucose (Prediabetes): 100-125 mg/dL (5.6-6.9 mmol/L)
• Diabetes: ≥126 mg/dL (≥7.0 mmol/L) 2

2-Hour Post-Load Glucose (OGTT)

• Normal: <140 mg/dL (<7.8 mmol/L)
• Impaired Glucose Tolerance (Prediabetes): 140-199 mg/dL (7.8-11.0 mmol/L)
• Diabetes: ≥200 mg/dL (≥11.1 mmol/L) 2

Random Plasma Glucose

• Diabetes: ≥200 mg/dL (≥11.1 mmol/L) with classic symptoms of hyperglycemia (polyuria, polydipsia, unexplained weight loss) 2

Clinical Significance of Blood Glucose Ranges

• Values between normal and diabetic ranges (prediabetes) indicate increased risk for developing diabetes and cardiovascular disease 2
• Individuals with fasting glucose levels even within the normal range but at the higher end (87-99 mg/dL) have an increased risk of developing type 2 diabetes compared to those with lower normal values 3
• The risk increases progressively with higher fasting glucose levels, even within the normal range 3

Special Considerations

Diagnosis Confirmation

• For diagnosis of diabetes, abnormal test results should be confirmed by repeat testing on a different day unless there is unequivocal hyperglycemia with acute metabolic decompensation 2
• If two different tests (such as FPG and A1C) are both above diagnostic thresholds, the diagnosis is confirmed 2

Biological Variation

• There is significant biological variation in glucose measurements - within-person CV of approximately 5.7% 2
• For a true fasting glucose of 100 mg/dL, the 95% confidence interval would be approximately 87-113 mg/dL when accounting for both biological and analytical variation 2

Hypoglycemia Classification

• Level 1: <70 mg/dL (3.9 mmol/L) but ≥54 mg/dL (3.0 mmol/L)
• Level 2: <54 mg/dL (3.0 mmol/L)
• Level 3: Severe event characterized by altered mental/physical status requiring assistance 2

Target Glucose Ranges for People with Diabetes

For many non-pregnant adults with diabetes, the American Diabetes Association recommends:

• Preprandial glucose: 80-130 mg/dL (4.4-7.2 mmol/L)
• Peak postprandial glucose: <180 mg/dL (<10.0 mmol/L) 2

Understanding normal glucose values is essential for early identification of metabolic disorders and for monitoring treatment effectiveness in those with diagnosed diabetes. These ranges help clinicians distinguish between normal glucose regulation, prediabetes, and diabetes, allowing for timely intervention to prevent complications related to hyperglycemia.