Blood Glucose Monitoring for Patients on Basal Insulin Plus One Oral Agent
For patients newly started on basal insulin with one oral agent (such as metformin), twice-daily blood glucose monitoring is recommended: fasting glucose plus one additional reading, ideally 2-hour postprandial. 1
Initial Monitoring Strategy
Frequency During Titration Phase
Perform twice-daily capillary blood glucose testing consisting of:
The fasting glucose measurement is the primary determinant for adjusting basal insulin doses, as it directly reflects overnight insulin coverage 1
Continue this frequency until HbA1c and blood glucose concentrations reach target goals and the patient remains asymptomatic 1
Rationale for Postprandial Testing
The 2-hour postprandial reading paired with premeal concentrations provides an index of glycemic excursion 1
This is particularly valuable when fasting plasma glucose appears normal but HbA1c remains above target, suggesting inadequate daytime glucose control 1
Postprandial monitoring helps identify whether the basal insulin regimen provides adequate coverage throughout the day or if additional mealtime intervention is needed 1
Evidence Quality and Context
Adult Guidelines
The 2022 American Diabetes Association Standards acknowledge that evidence is insufficient regarding optimal monitoring frequency for patients on basal insulin with oral agents 1
However, they confirm that assessing fasting glucose with blood glucose monitoring to inform dose adjustments results in lower A1C 1
The 2024 Standards reiterate this position, noting limited evidence for specific monitoring schedules in this population 1
Pediatric Guidelines
The 2013 Pediatrics guidelines provide more specific recommendations for youth with type 2 diabetes on this regimen 1
These recommendations are based on expert opinion (evidence quality D) but offer practical guidance applicable to clinical practice 1
Monitoring After Achieving Glycemic Control
Reduced Frequency Monitoring
Once treatment goals are met, monitoring frequency can be decreased based on clinical context 1
Consider the medication regimen, HbA1c levels, and patient willingness when determining ongoing monitoring frequency 1
Some continued blood glucose testing is recommended for all patients with type 2 diabetes, even after achieving targets 1
When to Increase Monitoring
Intensify monitoring during illness or if symptoms of hyperglycemia or hypoglycemia develop 1
Patients prone to marked hyperglycemia or hypoglycemia require continued frequent testing 1
Basal insulin carries some risk of hypoglycemia, especially overnight or fasting hypoglycemia 1
Common Pitfalls and Clinical Pearls
Inadequate Daytime Coverage
If fasting blood glucose concentrations are at target but daytime readings remain elevated, the basal-only regimen may be insufficient 1
In such cases, consider adding a meglitinide or short-acting insulin before meals 1
Hypoglycemia Detection
The basal insulin regimen is associated with risk of overnight or fasting hypoglycemia 1
Daily fasting measurements help detect this pattern early 1
Research shows that continuous glucose monitoring detects significantly more hypoglycemic episodes than point-of-care testing, particularly during nighttime 2, 3
Patient Education Requirements
Provide a written action plan stating the medication regimen, frequency and timing of expected blood glucose monitoring, and follow-up instructions 1
Set clear expectations through shared goal-setting between patient and clinician 1
Target fasting blood glucose of 70-130 mg/dL is reasonable for most patients 1
Alternative Monitoring Technologies
Continuous glucose monitoring (CGM) may be offered for adults on basal insulin who can use devices safely 1
CGM provides more comprehensive glycemic data and detects more hypoglycemic episodes than capillary monitoring alone 2, 3
However, patients using CGM still need capability to perform self-monitoring of blood glucose for calibration and verification 1