GLP-1 pen leftover calculator
How many doses are left in your GLP-1 pen?
A patient question nobody answers cleanly: at the dose you’re dialing, how many doses does your pen actually contain, how many are left, and when do you need a refill? This tool uses FDA-label fill volumes and dose counts for the multi-dose pens (Ozempic, Saxenda) and explains why the single-dose pens (Wegovy, Zepbound, Mounjaro) cannot be extended.
First: is your pen single-dose or multi-dose?
Single-dose pens
Wegovy · Zepbound · Mounjaro
Each pen delivers one weekly injection and is then discarded. There is no “leftover” — the device is engineered to dispense exactly one dose and cannot be re-used. Do not attempt to extract any residual liquid with a syringe.
Multi-dose pens
Ozempic · Saxenda
The patient dials each dose from a shared cartridge. Use the calculator below to track how many doses are left and when you’ll need a refill.
Multi-dose pen calculator
Use this for Ozempic and Saxenda. (Wegovy, Zepbound, and Mounjaro pens are single-dose — see the card above.)
Your pen, by the numbers
Total doses in this pen
4
at 1 mg per week
Doses remaining
4
0 taken
Volume remaining
3 mL
0.75 mL per dose
Days of supply remaining
28 days
weekly dosing
At your current schedule, this pen will run out around May 6, 2026. Plan your refill request 1–2 weeks ahead to avoid a gap in dosing.
Educational tool only — not medical advice. All fill volumes and dose counts are taken from the FDA prescribing information for each pen. Never attempt to extract drug from a pen with a syringe; sterility and dose accuracy cannot be guaranteed outside the pen’s metered mechanism.
Multi-dose GLP-1 pen reference table
From the FDA prescribing information for each pen. Total doses are computed as fill / dose volume rounded down — the dose-stop mechanism in the pen physically prevents dispensing beyond the labeled count.
| Pen | Fill | Dose | Doses per pen | Schedule |
|---|---|---|---|---|
| Ozempic 0.25/0.5 mg starter pen 2 mg / 3 mL | 3 mL | 0.25 mg | 4 | Weekly |
| 0.5 mg | 4 | Weekly | ||
| Ozempic 1 mg pen 4 mg / 3 mL | 3 mL | 1 mg | 4 | Weekly |
| Ozempic 2 mg pen 8 mg / 3 mL | 3 mL | 2 mg | 4 | Weekly |
| Saxenda 18 mg/3 mL pen 18 mg / 3 mL | 3 mL | 0.6 mg (week 1) | 30 | Daily |
| 1.2 mg (week 2) | 15 | Daily | ||
| 1.8 mg (week 3) | 10 | Daily | ||
| 2.4 mg (week 4) | 7 | Daily | ||
| 3.0 mg (maintenance) | 6 | Daily |
Why brand pens won’t let you “squeeze extra doses”
Every brand-name GLP-1 pen contains a small overfill — a manufacturing tolerance that ensures the labeled number of doses can always be delivered, even if a tiny amount is lost to priming or trapped in the cartridge deadspace. Patients sometimes notice this and ask whether they can dial one more dose.
The answer from the FDA labels is no, for two independent reasons:
- Mechanical stop. Multi-dose pens like Ozempic and Saxenda have a physical mechanism that prevents the dose dial from advancing past the labeled dose count once the cartridge has dispensed its rated volume. The dial will simply not turn far enough to inject another full dose.
- Dose accuracy not validated past the label. The overfill is not consistent enough to be a reliable dose. Manufacturing tolerance is on the order of a few percent — not enough for a full additional dose, but enough that any “bonus” injection would be a partial, unvalidated dose that could be far above or below the labeled mg.
What to do if you have leftover liquid
Discard the pen per the FDA label instructions. Do not attempt to draw the residual liquid out with an insulin syringe. Sterility cannot be guaranteed once the pen is opened to atmosphere, and the dose accuracy of a hand-drawn syringe from a brand pen has never been validated. If you’re running low between refills, contact your prescriber — most telehealth clinics will authorize an early refill or a bridge prescription.
Compounded vials are different
The rules above apply to brand-name pens. Compounded GLP-1 vials — sold as multi-use vials of semaglutide or tirzepatide reconstituted with bacteriostatic water — work on a totally different model. The patient draws each dose with an insulin syringe, and the “leftover” question becomes a units-conversion question. See our compounded GLP-1 reconstitution guide and the GLP-1 unit converter for the math.
Related research and tools
- GLP-1 storage and shelf life — refrigeration windows and 56-day room-temperature limits per FDA label
- Wegovy pen vs compounded vial — single-dose pens vs multi-use vials, end-to-end
- How to inject a GLP-1 step by step — injection technique for both pens and syringes
- GLP-1 unit converter — mg ↔ insulin syringe units for compounded vials
- GLP-1 washout calculator — how long the drug stays in your system after the last dose
Frequently asked questions
How many doses are in an Ozempic pen?
Per the FDA Ozempic label (Section 3 Dosage Forms and Strengths): the 0.25 mg/0.5 mg starter pen contains 2 mg of semaglutide in 3 mL and is labeled to deliver 4 weekly doses at either 0.25 mg or 0.5 mg. The 1 mg pen contains 4 mg in 3 mL and delivers 4 doses at 1 mg. The 2 mg pen contains 8 mg in 3 mL and delivers 4 doses at 2 mg. Each Ozempic pen is a 4-week supply at the labeled dose.
Can I get extra doses out of a Wegovy pen?
No. Wegovy is a single-dose prefilled pen — each pen delivers one weekly injection and is then discarded. Although the cartridge contains a small overfill for manufacturing tolerance, the device is designed to deliver exactly one dose and cannot be re-used. Do not attempt to extract additional drug with a syringe.
What do I do with leftover liquid in my Saxenda pen?
Discard the pen 30 days after first use, even if drug remains, because the preservative system is only validated for that period. Do not draw leftover liquid into a syringe — sterility and dose accuracy cannot be guaranteed outside the pen's metered mechanism. Contact your prescriber for a refill before you run low.
Is it safe to use a partial dose if I run out?
No. Multi-dose pens like Ozempic and Saxenda physically stop dialing once the labeled dose count is exhausted, and a partial dose from any GLP-1 pen is not validated for accuracy. If you run out before your refill arrives, contact your prescriber — do not improvise with syringes or by combining pens.
How long does an Ozempic pen last?
At the labeled weekly dose, every Ozempic pen is a 4-week supply: the 0.25 mg, 0.5 mg, 1 mg, and 2 mg pens each deliver 4 weekly doses. The 0.25 mg/0.5 mg starter pen lasts 8 weeks if you're still on the 0.25 mg starting dose. Once opened, a pen is good for 56 days at room temperature per the FDA label.
What if I dialed too much by accident?
Ozempic and Saxenda pens let you dial back without losing drug — turn the dial counter-clockwise until it shows the correct dose. If you've already injected an over-dose, contact your prescriber or poison control. Do not skip your next dose without clinical guidance — GLP-1 overdose protocols depend on which drug, how much, and your symptoms.
Important disclaimer
This tool is for educational purposes only and does not constitute medical advice. All fill volumes and dose counts are taken directly from the FDA prescribing information for each pen. If you have any question about whether your pen has a dose left, contact your prescribing clinician — do not improvise. Never attempt to extract drug from any single-dose or multi-dose pen with a syringe.
References
- 1.Novo Nordisk Inc. OZEMPIC (semaglutide) injection — US Prescribing Information, Section 3 Dosage Forms and Strengths and Section 16 How Supplied (multi-dose pen fill volumes and labeled dose counts). FDA Approved Labeling. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/209637s035,209637s037lbl.pdf
- 2.Novo Nordisk Inc. WEGOVY (semaglutide) injection — US Prescribing Information, Section 16 How Supplied (single-dose prefilled pen). FDA Approved Labeling. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/215256s026lbl.pdf
- 3.Novo Nordisk Inc. SAXENDA (liraglutide) injection — US Prescribing Information, Section 3 Dosage Forms and Strengths (18 mg/3 mL multi-dose pen). FDA Approved Labeling. 2024. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/206321s022lbl.pdf
- 4.Eli Lilly and Company. MOUNJARO (tirzepatide) injection — US Prescribing Information, Section 16 How Supplied (single-dose prefilled pen). FDA Approved Labeling. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/215866s039lbl.pdf
- 5.Eli Lilly and Company. ZEPBOUND (tirzepatide) injection — US Prescribing Information, Section 16 How Supplied (single-dose prefilled pen and single-dose vial). FDA Approved Labeling. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/217806s002lbl.pdf