Should Patients on Insulin Therapy Check Daily Capillary Blood Glucose?
Yes, patients on insulin therapy must check their capillary blood glucose (CBG) daily, with the frequency and timing determined by their insulin regimen intensity—those on intensive insulin therapy (multiple daily injections or insulin pump) should test 6-10 times daily, while those on basal insulin alone require less frequent monitoring focused primarily on fasting glucose. 1
Intensive Insulin Regimens (Multiple Daily Injections or Insulin Pump)
For patients on intensive insulin therapy, CBG monitoring is not optional—it is an integral component of safe and effective therapy. 1
These patients should test at minimum 6-10 times daily at the following critical timepoints: 1
- Before each meal and snack
- At bedtime
- Occasionally postprandially (after meals)
- Prior to exercise
- When hypoglycemia is suspected
- After treating hypoglycemia until normoglycemia is confirmed
- Prior to critical tasks such as driving
The evidence strongly supports this frequency: a database study of nearly 27,000 children and adolescents with type 1 diabetes demonstrated that each additional CBG check per day was associated with a 0.2% reduction in HbA1c and fewer acute complications. 1
Basal Insulin Only or Less Intensive Regimens
For patients using basal insulin with or without oral agents, the evidence for optimal monitoring frequency is less clear, but at minimum, fasting glucose monitoring is essential for dose titration. 1
The American Diabetes Association acknowledges that evidence is insufficient regarding exact frequency for these patients, but emphasizes that assessing fasting glucose with CBG to inform basal insulin dose adjustments results in lower HbA1c levels. 1
Critical Safety Considerations
CBG monitoring is especially critical for preventing both hypoglycemia and hyperglycemia in insulin-treated patients. 1
Common Pitfalls to Avoid:
Checking without action: Many patients who check glucose at least once daily report taking no action when results are abnormal—this renders monitoring useless. 1 Patients must be trained to use CBG data to adjust food intake, physical activity, or insulin doses. 1
Meter accuracy issues: Only FDA-approved meters with proven accuracy should be used, with unexpired strips purchased from licensed sources. 1 Providers must be aware that substantial variation exists in the accuracy of widely used BGM systems. 1
Inadequate technique: CBG accuracy depends on both the instrument and user technique, requiring evaluation at initiation and regular intervals thereafter. 1
Interference factors: High-dose vitamin C, hypoxemia, and certain medications can interfere with glucose meter accuracy. 1
Continuous Glucose Monitoring as an Alternative
While CGM can replace most CBG testing in appropriate patients, it does not eliminate the need for CBG entirely. 1 Patients using CGM must still have access to CBG for calibration (some sensors), when CGM accuracy is suspected, during sensor warm-up, and in situations where glucose is changing rapidly (>2 mg/dL/min). 1
Research demonstrates that CGM detects significantly more hypoglycemic episodes than CBG alone—in one study of hospitalized type 2 diabetes patients, CGM detected 55 hypoglycemic episodes compared to only 12 detected by point-of-care testing. 2
Practical Target for Patients
Achieving approximately 60% of CBG readings in the target range (4-10 mmol/L or 72-180 mg/dL) correlates with HbA1c <7.5% (<58 mmol/mol), with up to 30% of readings above target being acceptable. 3 This provides a more practical and less anxiety-provoking target than expecting all readings to be in range. 3
Special Insulin Considerations
The FDA label for insulin detemir (representative of basal insulins) explicitly states that "frequent, patient-performed blood glucose measurements are needed to achieve effective glycemic control to avoid both hyperglycemia and hypoglycemia." 4 Insulin requirements may change with illness, stress, emotional disturbances, inadequate food intake, or changes in physical activity, necessitating ongoing monitoring. 4