In a patient 5 hours after an insulin lispro overdose with a random blood glucose of 155 mg/dL, when should the next glucose measurement be performed?

Glucose Monitoring After Insulin Lispro Overdose

In a patient 5 hours after insulin lispro overdose with a current glucose of 155 mg/dL, repeat the glucose measurement in 1-2 hours, then continue hourly monitoring until glucose remains stable above 100 mg/dL for 2-3 consecutive readings. 1

Immediate Monitoring Protocol

• Check glucose every 1-2 hours until both glucose values and any dextrose infusion rates are stable, as recommended by the American College of Critical Care Medicine 1
• After stabilization is confirmed, extend monitoring intervals to every 4 hours 1
• Maintain hourly glucose checks if the patient is receiving IV dextrose or if any glucose measurement in the prior 4 hours fell below 70 mg/dL 1

Critical Context for This Case

At 5 hours post-overdose, you are approaching the tail end of lispro's duration of action (3-4 hours), but the overdose context means residual insulin activity may persist 2. The current glucose of 155 mg/dL is reassuring but does not eliminate hypoglycemia risk:

• Insulin lispro has a duration of 3-4 hours under normal dosing, with peak action at 1-2 hours 2
• In overdose situations, recurrent hypoglycemia is more likely when the overdose is substantial, the patient has inadequate oral intake, or renal impairment prolongs insulin clearance 1
• Continue hourly glucose monitoring for at least 5-6 hours post-overdose and until glucose has remained above 100 mg/dL for 2-3 consecutive readings without dextrose support 1

Hypoglycemia Treatment Thresholds

• Glucose < 70 mg/dL mandates immediate treatment with either 15-20 g of fast-acting carbohydrate (if alert) or 10-20 g of hypertonic (50%) dextrose IV (if mental status is altered) 1, 3
• After treating hypoglycemia, re-measure glucose after 15 minutes and repeat the intervention if the value remains below 70 mg/dL 1, 3
• Do not rely solely on patient-reported symptoms to detect hypoglycemia, because recurrent episodes can produce hypoglycemia unawareness 4, 1

Common Pitfalls to Avoid

• Do not extend monitoring intervals prematurely based on a single reassuring glucose value—the patient needs sustained stability above 100 mg/dL for 2-3 consecutive hourly readings before relaxing surveillance 1
• Do not overcorrect hypoglycemia with excessive dextrose (avoid boluses ≥25 g), as this creates glycemic variability which independently increases mortality risk 3
• A 25-g IV dextrose bolus typically raises glucose by approximately 63.5 ± 38.8 mg/dL at 15 minutes, with the effect often returning to baseline by 30 minutes, indicating rapid and variable fluctuations 1

Monitoring Duration Rationale

The Society of Critical Care Medicine recommends glucose monitoring every 1-2 hours until values and infusion rates are stable 1. In this overdose scenario, even though you are 5 hours out, the patient requires continued hourly checks because:

• Residual insulin activity may still be present from the overdose 1
• The current glucose of 155 mg/dL, while acceptable, does not guarantee stability over the next several hours 1
• Frequency of hypoglycemia should be determined at every visit, and presence of hypoglycemia unawareness should be assessed 4