How many Humalog (insulin lispro) 100 units/ml cartridges are needed for a month's supply for a patient taking 4 units before meals?

Humalog Cartridge Supply Calculation for 4 Units Before Meals

For a patient taking 4 units of Humalog before each meal (assuming 3 meals daily), you will need to dispense 2 cartridges (3 mL each) for a 30-day supply.

Calculation Breakdown

Daily insulin requirement:

• 4 units × 3 meals = 12 units per day 1

Monthly insulin requirement:

• 12 units/day × 30 days = 360 units total 1

Cartridge capacity:

• Each Humalog 100 units/mL cartridge contains 3 mL
• 3 mL × 100 units/mL = 300 units per cartridge 2

Number of cartridges needed:

• 360 units ÷ 300 units per cartridge = 1.2 cartridges
• Round up to 2 cartridges to ensure adequate supply 2

Clinical Context for This Dosing

• The 4 units per meal dose aligns with guideline recommendations for initiating mealtime insulin, which suggest starting at 4 units per meal, 0.1 units/kg per meal, or 10% of basal insulin dose per meal when HbA1c is less than 8% 1

• This prandial insulin regimen should be administered immediately before meals (within 0-15 minutes) due to Humalog's rapid onset of action at 5 minutes and peak effect at 1-2 hours 2, 3

Important Dispensing Considerations

Storage and handling:

• Unopened cartridges must be refrigerated at 36-46°F (2-8°C) 2
• Once in use, cartridges may be kept at room temperature to reduce injection site irritation 2
• Avoid temperatures below 36°F or above 86°F to prevent loss of potency 2

Patient education points:

• Inspect cartridges before each use; any clumping, frosting, precipitation, or change in clarity indicates loss of potency 2
• Patients should wear medical alert identification and consider glucagon prescription for emergency hypoglycemia 2