A patient with type 1 diabetes is starting insulin lispro (Humalog) as mealtime coverage. Which teaching point about timing of administration is MOST appropriate?

Question

Accepted Answer

✅ A. Inject insulin lispro within 0 to 15 minutes before starting a meal.

Insulin lispro (Humalog) is a rapid-acting analog insulin with an onset of 10-15 minutes, peak at 30-90 minutes, and duration of 3-5 hours. It should be injected 0-15 minutes before a meal (some patients dose immediately at the start of the meal, especially if meal size is uncertain). This matches the PK profile to post-prandial glucose absorption. Rapid-acting insulins include lispro, aspart, and glulisine.

❌ B. Inject insulin lispro 30 minutes before a meal, like regular insulin.
This is the timing for REGULAR (short-acting) insulin, which has onset ~30 minutes and must be given 30 minutes pre-meal to prevent post-prandial hypoglycemia. Rapid-acting analogs like lispro are much faster.

❌ C. Inject insulin lispro 60-90 minutes after finishing the meal to cover the glucose spike.
Post-meal injection is not standard practice and would produce late hypoglycemia, as the rapid insulin peak would arrive after blood glucose has already fallen.

❌ D. Inject insulin lispro only at bedtime for basal coverage.
Incorrect class. Lispro is rapid-acting (mealtime coverage). Bedtime basal coverage is provided by long-acting insulins such as glargine, detemir, or degludec.

:::pearl
Lispro / aspart / glulisine = RAPID-acting (0-15 min before meal). Regular insulin = SHORT-acting (30 min before meal). Don't confuse the two.
:::

Insulin Lispro

✅ Indications

⚙️ Mechanism of Action

📏 Dosing

🚫 Contraindications

⚠️ Adverse Effects

🔬 Monitoring

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