Vial economics
What your vial expires with still in it
A 10 mg vial holds forty 0.25 mg microdoses. It does not hold them for forty weeks. Once it is mixed, the discard date on the label starts running, and at a small enough dose that date arrives with most of the vial still in it — drug you have already paid for.
This is the cost nobody quotes you, and it only exists at the low end: a full-dose patient finishes the same vial inside the same window and wastes nothing.
Read before you use this
This is arithmetic, not medical advice, and it is not a reason to use a vial past its discard date. The date on your label was assigned by the pharmacy that compounded that preparation — we do not know it, we do not publish a figure of our own, and the value in the field below is a placeholder for you to overwrite. Intentional microdosing is off-label and unproven. Storage, handling and dosing belong to you and your prescriber.
- Doses in the vial
- 40
- 10 mg ÷ 0.25 mg
- Doses you can use
- 4
- before the 28-day discard date
- Weeks one vial covers
- 4
- 4 doses ÷ 1/wk
- Drug you take
- 1mg
- 4 × 0.25 mg
- Drug you bin
- 9mg
- 90% of the vial
- Vials per year
- 13.0
- at this dose and this discard window
At this dose the vial expires before you finish it: 40 doses are in there and you can reach 4. Add the vial cost above to see what the drug that reaches you actually costs per milligram.
Why the number is so large at a microdose
Vials are sized around the doses most patients take. At 2.5 mg weekly a 10 mg vial is four doses and roughly a month of therapy — a good match for a typical discard window. At 0.25 mg weekly the same vial is forty doses and ten months of therapy, and the window does not move. The mismatch is the waste, and it scales with how small your dose is: halve the dose and you double the proportion binned.
Three things change the answer and one does not. A smaller vial helps. A longer beyond-use date helps. A program that charges by the dose rather than a flat rate helps, and across the 373 providers on our review index 39 quote their figures off the lowest dose. Splitting the weekly amount across two injections does not — it changes the schedule, not the milligrams you get through.
It is worth being blunt about where this leaves our own tooling. The reconstitution calculator reports cost per milligram as the vial price divided by the vial contents. That is the standard figure and it is the optimistic one. Where a discard date bites, the number above is the one you are actually paying.
Common questions
- How long does a compounded semaglutide or tirzepatide vial last after mixing?
- There is no general answer, and anyone who gives you one without seeing your label is guessing. Beyond-use dating for a compounded preparation is assigned by the compounding pharmacy that made it, based on that formulation, its preservative and how it is stored, and it is printed on the vial. That is the number to put into this calculator. We deliberately do not publish a figure of our own, because the whole point of the tool is that this number changes the answer enormously and it has to be yours.
- Why does a microdose waste so much of the vial?
- Because vials are sized for full doses. A 10 mg vial holds forty 0.25 mg microdoses but only four 2.5 mg full doses. The full-dose patient finishes it inside a typical discard window; the microdoser reaches four doses before the same window closes and bins the remaining 9 mg. The vial is not the constraint at a low dose — the calendar is.
- Does splitting my dose across two days a week reduce the waste?
- No. Splitting changes how many injections you take, not how many milligrams you get through before the discard date — 0.25 mg twice weekly uses the same 0.5 mg a week that 0.5 mg once weekly does. It can make a small dose easier to draw accurately, which is a real advantage, but it does not recover any of the drug you would otherwise throw away. The calculator shows both schedules landing on the same milligrams used.
- Should I keep using a vial past its discard date to avoid the waste?
- No, and this calculator is not an argument for doing so. It exists to show you a cost you are already paying and probably cannot see, so that you can raise it with your prescriber and factor it into which program you buy. A smaller vial, a different concentration, or a provider that prices by dose rather than flat are all ways to reduce it. Using a preparation past the date its pharmacy assigned is not.
- How does this differ from the cost per mg in your reconstitution calculator?
- The reconstitution calculator divides the vial price by the milligrams in the vial, which is the cost of a milligram you have bought. This one divides by the milligrams you actually inject before the vial has to go, which is the cost of a milligram that reaches you. At a full dose the two are the same number. At a microdose they can differ by a factor of ten, and the second one is the one you are really paying.
Informational only and not medical advice. This tool performs arithmetic on figures you supply and knows nothing about your medication, your prescription or your storage conditions. It is not a recommendation to microdose, to change a dose, or to use any preparation beyond the discard date its compounding pharmacy assigned. Compounded GLP-1s are not FDA-approved. Talk to a licensed clinician.