What is the recommended frequency for checking capillary blood glucose for patients on insulin and oral hypoglycemic agents (OHAs), such as metformin, sulfonylureas, or pioglitazone?

Timing of Capillary Blood Glucose Monitoring

For Patients on Insulin

Patients on multiple daily insulin injections should check capillary blood glucose at least 3 times daily before meals and at bedtime, with many requiring 6-10 checks daily including before meals and snacks, at bedtime, occasionally postprandially, prior to exercise, when suspecting hypoglycemia, after treating hypoglycemia until normoglycemic, and before critical tasks like driving. 1

Intensive Insulin Regimens (Multiple Daily Injections or Pump)

• Check before each meal and snack to guide prandial insulin dosing 1
• Check at bedtime to assess overnight insulin needs and prevent nocturnal hypoglycemia 1
• Check occasionally 1-2 hours postprandially to assess meal coverage, particularly helpful in patients with gastroparesis or those using rapid-acting insulin to adjust dose-meal calculations 1
• Check prior to exercise to prevent exercise-induced hypoglycemia 1
• Check when suspecting hypoglycemia and continue checking after treatment until normoglycemic 1
• Check before critical tasks such as driving 1

This intensive monitoring schedule typically requires 6-10 or more checks daily, with frequency associated with better glycemic control (0.2% A1C reduction per additional daily check) 1

Basal Insulin Only (with or without oral agents)

• Check fasting glucose every morning as the primary determinant for adjusting basal insulin doses, since it directly reflects overnight insulin coverage 2, 3
• Add one additional reading daily, preferably 2-hour postprandial, which paired with premeal concentrations provides an index of glycemic excursion 2, 3

The American Diabetes Association acknowledges insufficient evidence for optimal monitoring frequency in this population, but confirms that assessing fasting glucose to inform dose adjustments results in lower A1C 1, 2, 3

Hospitalized Patients on Insulin

• For patients eating: Check immediately before each meal 1
• For patients not eating or NPO: Check every 4-6 hours 1
• For patients on intravenous insulin: Check every 30 minutes to 2 hours as required for safe titration 1

For Patients on Oral Hypoglycemic Agents Only

Patients on oral agents without insulin should check capillary blood glucose daily, with frequency sufficient to achieve glycemic goals, though optimal frequency has not been established and routine monitoring may provide limited additional clinical benefit. 1

Practical Monitoring Strategy

• Check fasting glucose to assess overnight glycemic control 2
• Consider occasional postprandial checks to understand the impact of meals and medications 1
• Frequency should be individualized based on medication type, glycemic stability, and treatment goals 1

Important Caveats for Oral Agents

• Evidence is insufficient regarding optimal monitoring frequency for patients on oral agents alone 1
• Several randomized trials question the clinical utility and cost-effectiveness of routine monitoring in noninsulin-treated patients 1
• Monitoring may provide insight into the impact of diet, physical activity, and medication management on glucose levels 1
• Once treatment goals are met, monitoring frequency can be decreased based on clinical context 3

Medications Requiring More Frequent Monitoring

• Sulfonylureas: Higher hypoglycemia risk warrants more frequent monitoring, especially if caloric intake is reduced 4
• Meglitinides: Similar to sulfonylureas, check before meals when used 3

Medications with Lower Monitoring Needs

• Metformin alone: Minimal hypoglycemia risk, less frequent monitoring acceptable 2
• Pioglitazone: Lower hypoglycemia risk compared to insulin secretagogues 5

Common Pitfalls to Avoid

• Never rely solely on sliding-scale insulin in hospitalized patients; use basal-bolus regimens with scheduled monitoring 1
• Suspect inaccurate readings if home blood glucose tests are inconsistent with A1C testing 2
• Ensure meter accuracy by using FDA-approved devices with unexpired strips from licensed distributors 2
• Hematocrit levels greatly influence test results; meters with hematocrit correction minimize this interference 2
• Other interfering substances include vitamin C, salicylic acid, uric acid, bilirubin, and triglycerides 2
• Temporarily withhold metformin in hospitalized patients with worsening renal function or before contrast imaging 4