Normal Blood Sugar Levels
Normal fasting blood 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). 1
Normal Blood Glucose Ranges
Blood glucose levels are classified into different categories based on standardized measurements:
Fasting Blood Glucose
- Normal: Less than 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) or higher on two separate occasions 1
Post-Meal (Postprandial) Blood Glucose
- Normal: Less than 140 mg/dL (7.8 mmol/L) at 2 hours after a meal
- Impaired Glucose Tolerance (Prediabetes): 140-199 mg/dL (7.8-11.0 mmol/L) at 2 hours after a 75g oral glucose tolerance test
- Diabetes: 200 mg/dL (11.1 mmol/L) or higher at 2 hours after a 75g oral glucose tolerance test 1
Random Blood Glucose
- Normal: Generally below 140 mg/dL (7.8 mmol/L)
- Diabetes: 200 mg/dL (11.1 mmol/L) or higher with symptoms of diabetes (polyuria, polydipsia, unexplained weight loss) 1
A1C Measurements
A1C reflects average blood glucose over the past 2-3 months:
- Normal: Less than 5.7%
- Prediabetes: 5.7-6.4%
- Diabetes: 6.5% or higher 1
Hypoglycemia Classification
Low blood sugar (hypoglycemia) is categorized into three levels:
- Level 1: Less than 70 mg/dL (3.9 mmol/L) but at least 54 mg/dL (3.0 mmol/L)
- Level 2: Less than 54 mg/dL (3.0 mmol/L)
- Level 3: Severe event characterized by altered mental and/or physical status requiring assistance 1, 2
Clinical Implications
Factors Affecting Blood Glucose
Blood glucose levels can fluctuate based on:
- Time since last meal
- Carbohydrate content of meals
- Physical activity level
- Stress
- Medications
- Illness 1
Hypoglycemia Management
If blood glucose falls below 70 mg/dL (3.9 mmol/L):
- Consume 15-20g of glucose (preferred) or any carbohydrate containing glucose
- Recheck blood glucose after 15 minutes
- Repeat treatment if glucose remains below 70 mg/dL
- Once glucose normalizes, eat a meal or snack if the next meal is more than an hour away 1, 2
Special Populations
- Elderly: May have different glucose targets due to risk of hypoglycemia
- Pregnant women: Different diagnostic criteria apply for gestational diabetes 1
Key Points to Remember
- Normal blood glucose levels maintain a relatively narrow range in healthy individuals
- Both consistently high and low blood glucose levels can lead to adverse health outcomes
- Regular monitoring is essential for those at risk of abnormal glucose levels
- The oral glucose tolerance test remains the gold standard for diagnosing impaired glucose metabolism, though fasting glucose and A1C are more commonly used in clinical practice 1