Should I administer a rescue dose of insulin for a patient with hyperglycemia who received 10 units of Insulatard (NPH insulin) 2 hours ago?

Should You Administer a Rescue Dose?

No, do not administer a rescue dose of rapid-acting insulin at this time—the blood glucose of 15.1 mmol/L (272 mg/dL) is expected 2 hours after NPH insulin administration, as NPH has not yet reached its peak effect, which occurs at 4-6 hours post-injection. 1

Understanding NPH Insulin Pharmacokinetics

NPH (Insulatard) is an intermediate-acting insulin with specific timing characteristics that are critical to understand:

• Onset of action: 1-2 hours after subcutaneous injection 2
• Peak effect: 4-6 hours after administration 2
• Duration: 12-16 hours total 2

Since only 2 hours have elapsed since the 10-unit NPH dose, the insulin has barely begun working and is nowhere near its peak effect. The current glucose of 15.1 mmol/L reflects the pre-insulin hyperglycemic state, not treatment failure.

When to Consider Correction Insulin

According to American Diabetes Association guidelines, supplemental correction insulin should be administered as follows: 1

• For non-critically ill hospitalized patients: Regular insulin can be given subcutaneously every 6 hours, or rapid-acting insulin analogs every 4 hours for hyperglycemia correction 1
• Dosing algorithm: For patients who are NPO, give supplemental regular insulin in 5-unit increments for every 50 mg/dL (2.8 mmol/L) increase above 150 mg/dL (8.3 mmol/L), up to 20 units for glucose of 300 mg/dL (16.7 mmol/L) 1

However, this correction dosing assumes you are using a basal-bolus regimen, not waiting for NPH to take effect. 3

Recommended Action Plan

Wait and monitor the glucose response:

• Recheck blood glucose in 2-4 hours (at the 4-6 hour mark post-NPH injection when peak effect occurs) 1
• If glucose remains >13.9 mmol/L (250 mg/dL) at 4-6 hours post-NPH, then consider adding correction insulin 3
• Monitor for hypoglycemia between 4-8 hours post-injection when NPH effect is strongest 2

Critical Pitfall to Avoid

Administering rapid-acting insulin now creates a dangerous "stacking" scenario: 3

• The NPH will reach peak effect in 2-4 hours
• If you give correction insulin now, both insulins will be active simultaneously
• This significantly increases hypoglycemia risk, particularly since the patient received a substantial 10-unit NPH dose
• Sliding scale insulin alone is strongly discouraged in hospitalized patients—if additional coverage is needed, transition to a proper basal-bolus regimen 3

When Immediate Correction IS Indicated

You should give correction insulin immediately only if: 1

• Glucose is >16.7-19.4 mmol/L (300-350 mg/dL) with symptoms of hyperglycemia or catabolic features 3
• Patient shows signs of diabetic ketoacidosis 1
• Patient is on continuous IV insulin protocol (different scenario entirely) 1

In this case with glucose of 15.1 mmol/L at 2 hours post-NPH, the appropriate action is watchful waiting with repeat glucose monitoring in 2-4 hours. 1