Tresiba FlexTouch 100 U/mL Pen Calculation for 90-Day Supply
You need 5 pens for a 90-day supply.
Calculation Breakdown
Daily insulin requirement:
- Morning dose: 25 units
- Evening dose: 25 units
- Total daily dose: 50 units 1
Total insulin needed for 90 days:
- 50 units/day × 90 days = 4,500 units total 1
Tresiba FlexTouch 100 U/mL pen specifications:
- Each pen contains 300 units (3 mL × 100 units/mL) 1
- The U-100 FlexTouch pen delivers doses in 1-unit increments and can deliver up to 80 units in a single injection 1
Number of pens required:
- 4,500 units ÷ 300 units per pen = 15 pens
Wait—this calculation appears incorrect based on the prescription showing "twice a day" dosing, which is not the FDA-approved dosing schedule for Tresiba.
Critical Prescribing Error Alert
Tresiba is FDA-approved for once-daily dosing only 1. The prescription as written ("twice a day") does not align with the approved administration schedule, which states: "In adults, inject TRESIBA subcutaneously once-daily at any time of day" and "In pediatric patients inject TRESIBA subcutaneously once-daily at the same time every day" 1.
If the prescription is corrected to once-daily dosing (50 units once daily):
- 50 units/day × 90 days = 4,500 units
- 4,500 ÷ 300 units per pen = 15 pens
If the prescription remains as written (25 units twice daily, though off-label):
- Same calculation: 15 pens
Important Dispensing Considerations
- Do not perform dose conversion when using Tresiba U-100 FlexTouch pens—the dose window shows the actual number of insulin units to be delivered 1
- Each pen is a single-patient-use device 1
- Pens in use should be discarded after 56 days, even if insulin remains 1
- For this 90-day supply, the patient will need to discard partially used pens at the 56-day mark 1
The prescriber should be contacted to clarify the twice-daily dosing, as this deviates from FDA-approved labeling for Tresiba 1.