How Long Does a Semaglutide Vial Last?

Last updated: June 2026

How long a semaglutide vial lasts comes down to one division: the total milligrams in the vial divided by your weekly dose gives the number of weeks of supply. A 10 mg compounded vial at 0.5 mg per week lasts 20 weeks of drug — but the in-use discard window your pharmacy or the label sets can end the vial sooner, whichever comes first.

Have a vial size and a weekly dose? Get exact weeks of supply, plus the mL and U-100 units per dose, in seconds.

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TL;DR — key takeaways

The core formula. Weeks of supply = total mg in the vial ÷ weekly dose in mg. A 5 mg vial at 0.25 mg/week = 20 weeks of drug.
Concentration doesn't change the weeks — only the units. Total mg sets how many doses you get; mg/mL sets how many syringe units each dose draws.
Two clocks run at once. The maths clock (doses remaining) and the stability clock (in-use discard / beyond-use date). The vial ends at whichever runs out first.
Titration shortens early vials. If your dose steps up every 4 weeks, a single vial spans fewer weeks than a flat-dose estimate suggests.
This is education, not medical advice. Always follow your prescriber's dose and the discard date printed on your vial.

The one formula that answers the question

A vial holds a fixed amount of drug, measured in total milligrams. Your weekly dose is also in milligrams. Divide one by the other and you have the number of weekly doses the vial physically contains:

Weeks of supply = total mg in vial ÷ weekly dose (mg)

Notice what is not in that equation: concentration. A vial labelled “10 mg” contains 10 mg of semaglutide whether it was reconstituted to 5 mg/mL or 10 mg/mL. The concentration changes how many syringe units you draw per dose, not how many doses are inside. That is the single most common point of confusion, so the worked examples below separate the two cleanly.

Worked examples — weeks of supply

Each example uses the same formula. Compounded semaglutide is commonly supplied in total amounts such as 2.5, 5, 10, 12.5, or 15 mg per vial; confirm yours against the label.

Example 1 — starter vial

A 5 mg vial at the 0.25 mg/week starting dose.

5 mg ÷ 0.25 mg/week = 20 weeks of drug.

Example 2 — mid-titration

A 10 mg vial at 0.5 mg/week.

10 mg ÷ 0.5 mg/week = 20 weeks of drug.

Example 3 — maintenance dose

A 10 mg vial at the 1 mg/week maintenance dose.

10 mg ÷ 1 mg/week = 10 weeks of drug.

Example 4 — top maintenance dose

A 12.5 mg vial at the 2.4 mg/week top maintenance dose.

12.5 mg ÷ 2.4 mg/week = 5.2 weeks — about 5 full doses with a small remainder.

Example 5 — units do not change the weeks

The same 10 mg vial at 0.5 mg/week still lasts 20 weeks whether it is 5 mg/mL or 10 mg/mL.

At 5 mg/mL: 0.5 ÷ 5 = 0.1 mL = 10 units per dose. At 10 mg/mL: 0.5 ÷ 10 = 0.05 mL = 5 units per dose. Fewer units, identical 20-week supply.

Example 6 — cross-check by volume

A 10 mg vial reconstituted to 5 mg/mL holds 2 mL of liquid. At 0.1 mL per dose that is 2 ÷ 0.1 = 20 doses — the same answer the mg formula gives, confirming the maths.

Example 7 — titration shortens a vial

A 10 mg vial used across a real titration: 4 weeks at 0.25 mg (1 mg) + 4 weeks at 0.5 mg (2 mg) = 3 mg used in 8 weeks, leaving 7 mg.

If the next phase is 1 mg/week, the remaining 7 mg lasts 7 more weeks — so the vial spans 15 weeks, not the 20 a flat 0.5 mg estimate would suggest.

Weeks-of-supply reference chart

Weeks of drug for common compounded vial sizes at each standard weekly dose. Values are total mg ÷ weekly dose, rounded down to whole doses where a remainder is too small for a full dose. Always confirm against your own label and prescriber's plan.

Weekly dose	5 mg vial	10 mg vial	12.5 mg vial	15 mg vial
0.25 mg (start)	20 wk	40 wk	50 wk	60 wk
0.5 mg	10 wk	20 wk	25 wk	30 wk
1 mg	5 wk	10 wk	12 wk	15 wk
1.7 mg	2 wk	5 wk	7 wk	8 wk
2.4 mg (max)	2 wk	4 wk	5 wk	6 wk

The chart shows drug supply only. In practice the in-use discard window (below) can cut a vial short well before the drug runs out — particularly the long runs in the top-left, where a 5 mg vial at 0.25 mg would otherwise stretch across 20 weeks.

The second clock: in-use discard and beyond-use dates

The maths above tells you how many doses are inside the vial. It does not tell you how long the vial is safe to keep using once opened. Two different limits apply, and the vial ends at whichever you reach first.

For branded pen products, the manufacturer sets an in-use window. The Ozempic and Wegovy prescribing information define a fixed number of days a pen may be used after first use before it must be discarded, alongside refrigerated and room-temperature storage limits — read the days printed on your specific product, not a number from a forum.

For compounded multi-dose vials, the relevant concept is the beyond-use date (BUD) assigned by the compounding pharmacy, plus general CDC guidance that opened multi-dose vials should be discarded when sterility is compromised or questionable. A vial with 12 weeks of drug left but a 28-day BUD must be discarded at 28 days. The maths does not override the label.

Example 8 — the discard date wins

A 5 mg vial at 0.25 mg/week has 20 weeks of drug — but if the pharmacy's BUD is 28 days, you use roughly 4 doses (1 mg) and discard the remaining ~4 mg unused. The drug clock said 20 weeks; the stability clock said 4.

How this is calculated

Every figure on this page uses two facts and nothing else. First, total drug divided by weekly dose gives weekly doses — pure arithmetic, identical for any vialled injectable. Second, to convert a dose into syringe units you divide the dose by the concentration (mg/mL) to get mL, then multiply by 100, because a U-100 syringe holds 100 units per mL. There is no semaglutide-specific constant; the calculator on this site automates exactly these steps so you can sanity-check a vial against the chart above. None of this decides whether a dose is right for you — that is your prescriber's call.

Frequently asked questions

Does a higher-concentration vial last longer?

No. Weeks of supply depend only on total milligrams and your weekly dose. A 10 mg vial lasts the same number of weeks at 5 mg/mL or 10 mg/mL — the stronger concentration just means you draw fewer units per dose.

Why does my vial run out faster than the chart says?

Usually titration. The chart assumes one flat weekly dose, but if your dose steps up every four weeks you consume more drug over time, so a single vial spans fewer weeks. Drawing extra to clear dead space or priming also uses drug.

What if the discard date arrives before the vial is empty?

Discard it. The in-use window on a pen label, or the beyond-use date your compounding pharmacy assigns, is a sterility and stability limit. Remaining drug does not extend it — follow the printed date.

How do I turn weeks of supply into units per injection?

That is a separate calculation based on concentration: dose ÷ mg/mL × 100 = units on a U-100 syringe. The semaglutide units calculator guide walks through it, or use the calculator for instant numbers.

Sources

This guide is for general educational purposes only and does not constitute medical advice. Always follow your prescriber’s specific instructions and consult a qualified clinician before changing any protocol.