Normal Capillary Blood Glucose Levels
The normal range for capillary blood glucose (CBG) levels in nonpregnant adults is 80-130 mg/dL (4.4-7.2 mmol/L) when fasting and less than 180 mg/dL (10.0 mmol/L) at peak postprandial measurements. 1
Normal Blood Glucose Ranges
For Nonpregnant Adults
- Fasting/preprandial capillary plasma glucose: 80-130 mg/dL (4.4-7.2 mmol/L) 1
- Peak postprandial capillary plasma glucose: <180 mg/dL (10.0 mmol/L) 1
- Postprandial measurements should be taken 1-2 hours after the beginning of a meal, when glucose levels typically peak 1
For Pregnant Women with Gestational Diabetes
- Preprandial: ≤95 mg/dL (5.3 mmol/L) 1
- 1-hour postmeal: ≤140 mg/dL (7.8 mmol/L) 1
- 2-hour postmeal: ≤120 mg/dL (6.7 mmol/L) 1
Continuous Glucose Monitoring Data in Healthy Individuals
Recent research using continuous glucose monitoring in healthy, nondiabetic individuals shows:
- Mean average glucose: 98-99 mg/dL (5.4-5.5 mmol/L) for most age groups 2
- Slightly higher average glucose (104 mg/dL or 5.8 mmol/L) in adults over 60 years 2
- Median time spent between 70-140 mg/dL (3.9-7.8 mmol/L): 96% of the day 2
- Median time with glucose >140 mg/dL: only 2.1% (approximately 30 minutes per day) 2
- Median time with glucose <70 mg/dL: only 1.1% (approximately 15 minutes per day) 2
Hypoglycemia Thresholds
- Level 1 hypoglycemia: <70 mg/dL (3.9 mmol/L) and ≥54 mg/dL (3.0 mmol/L) 1
- Level 2 hypoglycemia (clinically significant): <54 mg/dL (3.0 mmol/L) 1
- Level 3 hypoglycemia: Severe event characterized by altered mental and/or physical status requiring assistance 1
- Treatment should be initiated at ≤70 mg/dL (3.9 mmol/L) with 15-20g of glucose 1
Important Considerations for Capillary Blood Glucose Testing
- Capillary blood glucose measurements may differ from venous plasma glucose measurements 1, 3
- In healthy individuals, capillary glucose readings tend to be slightly higher than venous readings (by approximately 0.3 mmol/L or 5.4 mg/dL) 3, 4
- The first capillary blood drop typically shows the lowest mean difference to plasma blood glucose concentrations (+4.92 mg/dL; +0.27 mmol/L) 4
- Accuracy of capillary testing may be affected by several factors including hematocrit, peripheral circulation, and shock states 1
- In critically ill patients, capillary blood testing may be inaccurate, with frequent false elevations, especially in hypoglycemic and hyperglycemic ranges 1
Clinical Implications
- For diabetes management, achieving 60% or more readings within the target range (4-10 mmol/L or 72-180 mg/dL) is associated with good glycemic control (HbA1c <58 mmol/mol or <7.5%) 5
- When using capillary blood glucose for screening purposes in epidemiological studies, it shows good correlation with venous plasma glucose (correlation coefficient of 0.681 for fasting and 0.897 for 2-hour post-glucose load) 6
- Capillary blood glucose is a feasible alternative for screening of diabetes and impaired glucose tolerance in settings where venous sampling may be difficult 6