Vial duration

Semaglutide vial duration calculator

Estimate how many weeks one 5 mg Semaglutide vial covers at your dose and weekly cadence.

iPhone · Free to download

Last updated: May 13, 2026

Vial (mg)

Dose (mg)

Doses / week

Total doses

Lasts

20 weeks

Semaglutide weeks-of-supply at common cadences

How long one 5 mg Semaglutide vial covers at a 0.25 mg per dose, for three weekly cadences. Total doses per vial: 20.

Doses per week	Total doses per vial	Weeks of supply
1	20	20.0
1	20	20.0
2	20	10.0

Math weeks-of-supply assumes every dose draws cleanly. Stability typically caps a reconstituted vial at 4–6 weeks of refrigerated use regardless of how much liquid remains.

Worked example

How long one Semaglutide vial lasts, the long version

Total doses in the vial: floor(5 ÷ 0.25) = 20. The floor matters — a partial dose at the bottom doesn't count.
Cadence: 1 dose per week for Semaglutide at this example step.
Math weeks-of-supply: 20 ÷ 1 = 20.0 weeks of liquid in the vial.
Stability ceiling: most reconstituted peptides are typically used within 4–6 weeks of refrigerated storage. Whichever number is smaller is the one that binds your refill date.
Doubling the dose roughly halves both numbers — and titration usually closes the gap between "math weeks" and "stability weeks" without you noticing.

Scenarios people actually run into

Three things that come up logging Semaglutide

Math says one 5 mg Semaglutide vial covers 20.0 weeks at 0.25 mg per dose. Stability typically caps a reconstituted vial at 4–6 weeks. Whichever number is smaller is the date on your refill calendar.
Titration up doubles the dose and halves the vial. A 12-week-on-paper vial becomes a 6-week vial the day you step up — order the next vial the same day you take the step.
Shipping windows are the silent third constraint. If your supplier runs 1–3 weeks, the refill order has to leave at least that long before "math weeks" or "stability weeks," whichever is binding.

Same-category neighbor

Semaglutide next to Retatrutide

Both sit in the GLP-1 bucket — here's the vial duration math side by side on each one's example vial.

	Semaglutide	Retatrutide
Vial	5 mg	10 mg
Cadence	1/wk	1/wk
Weeks of supply	20.0	5.0

Want the full breakdown? Retatrutide reference →

Semaglutide is a once-a-week injection people use to lose weight and steady blood sugar. It mimics a gut hormone called GLP-1, which makes you feel full sooner and slows how fast your stomach empties. In the STEP-1 trial, adults without diabetes lost about 14.9% of their body weight over 68 weeks on the highest dose. This page covers the reconstitution math and how people log each weekly dose.

Planning Semaglutide vials in real life

Semaglutide is the easiest peptide to plan refills for, because the cadence is fixed — one dose per week, same day, same time. The math has only two moving parts: vial size and dose step. A 5 mg vial covers 20 weeks at 0.25 mg, 10 weeks at 0.5 mg, 5 weeks at 1 mg, and roughly 2 weeks at the 2.4 mg maintenance dose. Pin those four numbers in your head and you'll always know which vial you're on.

The catch is the stability ceiling. A reconstituted semaglutide vial is typically used within 4-6 weeks once it has bacteriostatic water in it. Math says a 5 mg vial at 0.25 mg lasts 20 weeks — stability says 5. That mismatch is why low-dose semaglutide users often reconstitute with 1 mL instead of 2 mL: more concentrated solution, same total doses, but they finish each vial inside the stability window.

Storage and shelf life for Semaglutide

Lyophilized semaglutide powder is generally stored refrigerated until reconstitution. Once reconstituted with bacteriostatic water, the in-use vial is typically kept refrigerated and used within four to six weeks. Writing the reconstitution date directly on the vial is one of the simplest ways to avoid running a long-opened vial past its useful life.

Light exposure and repeated temperature cycling both reduce stability. Storing the vial in the door of a refrigerator — where temperature swings most each time the door opens — is a common avoidable mistake.

How the Semaglutide vial duration calculator works

A 5 mg semaglutide vial covers 20 weekly doses at the 0.25 mg starter step. Drop to a 0.5 mg step and that becomes 10 weeks. Move to a 1 mg step and you're at 5 weeks. Knowing this before you reconstitute is what stops you running dry mid-titration.

The formula is two divisions. Total doses per vial equals vial mg divided by dose mg, rounded down. Weeks of supply equals total doses divided by doses per week. With a 5 mg vial of Semaglutide, a 0.25 mg dose, and 1 dose per week, the vial covers 20 doses, or about 20.0 weeks of supply.

The three inputs that move the answer: vial mg (set when you bought the vial), dose mg (set by your protocol step), and doses-per-week (set by the peptide's half-life). Once a vial is reconstituted it also has a stability ceiling — most lyophilized peptides reconstituted in BAC water are typically used within four to six weeks of refrigerated storage, so a vial that mathematically lasts twelve weeks may not last twelve weeks in practice.

Common Semaglutide vial-planning mistakes

Storing reconstituted semaglutide at room temperature for hours before refrigerating, especially after a travel day.
Switching to a new vial of the same peptide and reusing the old unit count without re-running the calculation against the new vial's diluent volume.
Dosing twice in the same week after forgetting whether the previous injection was Sunday or Monday — almost always a logging-gap problem, not a math problem.

Frequently asked questions about Semaglutide vial duration

How does the Semaglutide vial duration calculator estimate weeks of supply?

It floors total doses (vial mg ÷ dose mg) then divides by doses per week. For this Semaglutide example — a 5 mg vial, 0.25 mg per dose, 1 dose/week — that's floor(5 ÷ 0.25) ÷ 1 = about 20.0 weeks. Flooring matters: a partial dose left in the vial doesn't count. Plan a refill order at the 4-week mark — semaglutide shipping typically runs 1-3 weeks.

Should I plan refills around the math, or around stability?

Whichever runs out first. Math says Semaglutide at the example dose lasts the calendar weeks shown above. Stability says most reconstituted peptides are typically used within 4–6 weeks of refrigerated storage regardless of how much liquid is left. If the math says 12 weeks but stability caps at 5, plan around 5 — and reconstitute the next vial with less water so you finish it in the stability window. Plan a refill order at the 4-week mark — semaglutide shipping typically runs 1-3 weeks.

Does titrating the Semaglutide dose up shorten vial life?

Yes, often dramatically. Doubling the dose halves the doses-per-vial. The calculator shows real-time how a step-up changes the weeks-of-supply line, so you can re-time refill orders before a titration event rather than discovering the gap mid-protocol. Plan a refill order at the 4-week mark — semaglutide shipping typically runs 1-3 weeks.

What if I take Semaglutide less often than the default cadence here?

Drop the doses-per-week field. With 1 dose/week the example vial lasts about 20.0 weeks; halving the cadence roughly doubles that, but you'll hit the stability ceiling first. A vial that mathematically covers 16 weeks rarely covers 16 weeks in practice. Plan a refill order at the 4-week mark — semaglutide shipping typically runs 1-3 weeks.

Related on Peptide Pilot

Track Semaglutide vials automatically

iPhone · Free · No credit card