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How long will my vial last?
The vial's mg divided by your dose is the doses it holds; times the days between doses, that's how long it lasts. A 10 mg vial at 250 mcg once a day holds 40 doses: 40 days.
Your vial and dose
Example numbersThis vial holds
40dosesat 250 mcg
- Days of supply
- 40 days
- Last dose
- Nov 30, 2026Monday
Past 28 days. The CDC’s limit for an opened multi-dose vial is 28 days unless its maker states another date: check your mixed vial.
In PepVaultPepVault’s Vials tab counts down the doses left in each vial as you log, shows the day it runs out, and marks it when it’s time to reorder.How the count works
A vial holds its labelled mass, so the count is plain division: doses = vial mg × 1,000 ÷ dose in mcg, dropping any part of a dose. The days are the doses times the days between them: once a day is 1, twice a day ½, three times a week about 2⅓.
The water you mix with doesn’t change the count. It sets the concentration, which decides how many units each dose fills on the syringe: the reconstitution calculator works that out.
Example: a 10 mg vial at 250 mcg once a day holds 40 doses, 40 days of supply.
A weekly shot works the same way: a 10 mg vial at 2.5 mg once a week holds 4 doses, 4 weeks of supply.
A mixed vial also has a clock. Once a needle has gone in, the CDC’s limit for a multi-dose vial is 28 days unless its maker states another date, so a vial that would last longer meets that date first.
Questions
Does adding more water give me more doses?
No. The water sets how concentrated the vial is, so it changes how many units each dose fills on the syringe, never how many doses the vial holds. The count is the vial’s mg divided by your dose.
How many doses are in a 10 mg vial?
At 250 mcg a dose, 40; at 500 mcg, 20; at 2.5 mg, 4. Divide 10,000 mcg by your dose in mcg and drop any part of a dose.
Sources
- CDC, Preventing Unsafe Injection PracticesMulti-dose vials: the 28-day limit once a vial is opened, after the USP’s General Chapter 797, unless the maker states another date (page dated Mar 26, 2024).
The count is arithmetic on your own numbers. The 28-day limit’s source, checked Oct 19, 2026.
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