GLP-1 Pen Supply Duration

Know exactly how long each GLP-1 pen will last. Input the milligrams in a prefilled pen and your prescribed weekly dose to calculate weeks of therapy per pen, pens needed in a 30-day month, and optional spend if you add the pen cost. A wastage field lets you mirror priming losses and residual fluid that never dispenses.

Enter the total milligrams in one prefilled pen (e.g., 3 mL × 6 mg/mL = 18 mg).
Dose prescribed per week after titration.
Optional. Defaults to $0.00 if blank to isolate supply duration only.
Optional. Defaults to 2% to reflect priming and unusable medication left in the pen.

Educational calculator only. Follow your prescriber's dosing instructions and consult your care team before adjusting medication schedules.

Examples

  • 18 mg pen, 2.4 mg weekly dose, $925 pen cost, 2% wastage ⇒ Weeks of therapy per pen: 7.35 weeks (51.5 days) • Pens required per 30-day month: 0.59 pens • Effective mg delivered per pen after wastage: 17.64 mg • Estimated medication spend: $544.82 USD per month ($6,537.80 USD per year).
  • 12 mg compounded vial used at 1.7 mg weekly, no cost entered, 5% wastage ⇒ Weeks of therapy per pen: 6.71 weeks (47.0 days) • Pens required per 30-day month: 0.65 pens • Effective mg delivered per pen after wastage: 11.40 mg • Medication cost left blank — only duration metrics shown.

FAQ

Do I include the priming dose in weekly injections?

Yes. Enter the clinical dose ordered by your prescriber. The wastage field handles priming clicks and residual fluid so you do not have to inflate the weekly dose.

What if I change doses mid-month?

Run the calculator for each dose level and average the pens-per-month output across the number of weeks you spend at each step in your titration schedule.

Can I compare pens from different manufacturers?

Absolutely. Enter each pen's mg content and price separately to see which offers the longest duration or lowest monthly cost at the same clinical dose.

Does the cost estimate include dispensing fees?

No. Add pharmacy dispensing fees or shipping charges to the pen cost input if you want them reflected in the monthly and annual spend outputs.

Additional Information

  • Most branded GLP-1 pens hold between 8 and 18 mg—check the label to avoid underestimating supply.
  • Wastage covers priming clicks, final drops that remain in the cartridge, or misfires; keep it low if you rarely waste medication.
  • Pens-per-month uses 30.4375 days (the average month) so multi-month scripts line up with pharmacy refill policies.
  • Add your pen price to compare cash pay versus insurance coverage or to project annual HSA needs.

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