Vial supply calculator
How many doses are really in your vial, the date you run out, and the date to reorder so you do not skip a week.
Read this first. This is arithmetic on the numbers you enter. It does not know your actual vial, your prescriber's plan, or your pharmacy's lead time. Confirm the concentration and quantity printed on your own vial, and order earlier than you think you need to.
Printed on the vial or the pharmacy paperwork.
Counting the first dose as week 1.
How long your pharmacy actually takes, including any prior authorisation. Be pessimistic.
Every dose in this vial
Why a titration step breaks the simple division
If you are holding a steady dose, a vial lasts total milligrams divided by dose. Once a step up lands partway through, that stops being true, because every dose after the increase eats the vial faster.
A 10 mg vial at 2.5 mg weekly is four doses and four weeks. The same vial, stepping to 5 mg at week 3, gives you two doses at 2.5 mg and one at 5 mg, and the vial is empty. Three doses, not four, and the week you thought you had covered is the week you find out.
The date that actually matters
Not the run-out date. The reorder date, which is the run-out date minus however long your pharmacy really takes. Prior authorisation, shortages and shipping all live in that gap, and the gap is where people end up skipping a week.
If your lead time varies, use the worst case you have actually experienced, not the one you were quoted.
Two things this cannot know
Beyond-use dating
A compounded vial usually carries a beyond-use date after it is first punctured, commonly 28 days, sometimes longer depending on the pharmacy and the preservative. If your vial holds more doses than that window allows, the limit is the date, not the milligrams. That date is on your label and it overrides this arithmetic.
Drawing losses
Some volume is left in the syringe hub and the vial every time. Over several draws that adds up to a fraction of a dose, which is why a vial that should hold exactly four sometimes yields three and a bit. Do not plan your last dose to the millilitre.
Common questions
- How many doses are in a 10 mg vial?
- At 2.5 mg per injection, four. At 5 mg, two. If your dose increases partway through, count the doses at each dose level separately, because the total is not a simple division.
- When should I reorder my GLP-1?
- Work back from your run-out date by your pharmacy's real lead time, including prior authorisation. Ten days is a common minimum and shortages make it longer.
- How long does a compounded vial last once opened?
- The beyond-use date on your label governs, commonly 28 days after first puncture. If the vial holds more doses than that window allows, the date is your limit, not the amount of medication left.
- What if I run out before my refill arrives?
- Contact your prescriber rather than stretching doses or splitting them. A gap of two or more weekly doses commonly means restarting lower, which the missed dose page covers.
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