Key takeaways
- Doses per vial = vial ÷ dose, rounded down. 10 mg at 250 mcg is 40 doses.
- Days a vial lasts = whole doses × days between doses. Every other day means 2 days between doses.
- The 28-day clock starts at first puncture, which is the day you mix, not the day of the first dose.
- The product label overrides the default. Some labels allow 28 days; some allow 14 or require immediate use.
- If a vial outlasts its beyond-use date, a smaller vial avoids waste without changing the dose.
How to use the doses per vial calculator
The calculator works out two dates and compares them: the day your vial runs out and the day it must be thrown away. Whichever comes first sets how many doses you actually get.
- Enter the vial and your dose. Use the total mg printed on the label and the amount per injection from your prescription.
- Choose how often. Pick a preset, or Custom for anything else. Twice daily is 14 doses per week.
- Enter the date mixed. It defaults to today. Change it if you mixed the vial earlier.
- Set the beyond-use period. Keep 28 days unless your product label or pharmacist gives a different in-use period.
- Add loss, if you want. Open Units and dead-space loss, enter the water you added and the units you lose per injection.
- Read the verdict and the timeline. Green means the vial runs out first. Red means some doses will expire, and the tool shows how many.
The doses per vial formula
Three steps turn a vial and a schedule into dates. The only rounding is in step 1, because a partial dose cannot be drawn as a full one.
Loss is optional. Loss in mcg = loss units ÷ 100 × concentration (mcg/mL).
Day 0 is the mix date. A dose that falls on the beyond-use date or later counts as expired.
| Variable | Meaning | Where to find it |
|---|---|---|
| Vial | Total peptide in the vial, mg (× 1,000 for mcg) | Vial or box label |
| Dose | Amount per injection | Your prescription |
| Loss | Liquid wasted per injection, in syringe units | Your syringe and technique; 0 if unknown |
| Doses per week | Frequency as a number | Daily = 7, every other day = 3.5 |
| BUD days | In-use period after first puncture | Product label; 28 days by default |
What is a beyond-use date?
A beyond-use date (BUD) is the date after which an opened or compounded preparation should not be used. It is different from the expiration date printed by the manufacturer, which applies to the sealed product.
For multiple-dose vials, the rule most people meet is 28 days. The CDC says an opened or needle-punctured multi-dose vial should be dated and discarded within 28 days unless the manufacturer states another date, and that the BUD should never go past the original expiration date. USP General Chapter <797>, official since November 1, 2023, sets the same limit for pharmacies. Its FAQ explains that a conventionally manufactured multiple-dose vial may not be used more than 28 days after first puncture unless its labeling says otherwise, and that a compounded multiple-dose preparation must not be used for longer than its assigned BUD or 28 days, whichever is shorter.
The limit exists mainly because every needle puncture is a chance to introduce microbes. Multiple-dose vials usually contain a preservative, such as the 0.9% benzyl alcohol in bacteriostatic water. The CDC notes that a preservative limits bacterial growth but does not give complete protection.
Running out vs expiring: two vials on one schedule
The same dose and schedule can end in two different ways depending on vial size. Both vials below were mixed on Sep 27, 2026 and used at 250 mcg daily with a 28-day BUD. Teal dots are usable doses; red dots fall on or after the BUD.
5 mg vial: runs out first
10 mg vial: expires first
How long do peptides last in the fridge?
After mixing, a peptide lasts as long as its label says, stored the way its label says. There is no single number for all peptides, because stability depends on the molecule, the formulation and the diluent. These FDA-approved labels show how much the in-use period can differ, even for the same drug.
| Product or rule | After mixing | Storage |
|---|---|---|
| Humatrope cartridge (somatropin) | Up to 28 days | Refrigerated 2–8 °C (36–46 °F); avoid freezing; protect from light |
| Serostim 4 mg vial with bacteriostatic water | Up to 14 days | Refrigerated 2–8 °C (36–46 °F) |
| Serostim 5 mg or 6 mg vial with sterile water | Use immediately; discard the rest | Single-dose vial |
| Any multiple-dose vial without a stated period | 28 days after first puncture | As labeled (USP <797>, CDC) |
The Serostim rows show why the diluent matters. Sterile water has no preservative, so a vial mixed with it is treated as single-use. Before mixing, a lyophilized (freeze-dried) vial follows its own label storage and expiration date; the in-use clock has not started. Many research peptides have no FDA label and no tested in-use period at all, so the 28-day default is a ceiling, not evidence that the peptide is still potent on day 27.
Doses per vial chart
Find your vial size on the left and your dose across the top. Each cell is the number of whole doses, before any dead-space loss. The water volume does not change these numbers.
| Vial | 100 mcg | 250 mcg | 500 mcg | 1 mg | 2 mg | 2.5 mg | 5 mg |
|---|---|---|---|---|---|---|---|
| 2 mg | 20 | 8 | 4 | 2 | 1 | — | — |
| 5 mg | 50 | 20 | 10 | 5 | 2 | 2 | 1 |
| 10 mg | 100 | 40 | 20 | 10 | 5 | 4 | 2 |
| 15 mg | 150 | 60 | 30 | 15 | 7 | 6 | 3 |
| 20 mg | 200 | 80 | 40 | 20 | 10 | 8 | 4 |
| 30 mg | 300 | 120 | 60 | 30 | 15 | 12 | 6 |
A dash means one dose is larger than the whole vial. Leftovers smaller than a dose are not counted.
How long does a vial last at each frequency?
This table takes one 5 mg vial at 250 mcg per dose, 20 doses, and applies a 28-day BUD. The less often you dose, the more of the vial is left when the BUD arrives.
| Frequency | Doses / week | Vial would last | Doses before BUD | Doses expiring | mg expiring |
|---|---|---|---|---|---|
| Daily | 7 | 20 days | 20 | 0 | 0 |
| Every other day | 3.5 | 40 days | 14 | 6 | 1.5 |
| 5× per week | 5 | 28 days | 20 | 0 | 0 |
| 3× per week | 3 | 46.7 days | 12 | 8 | 2 |
| 2× per week | 2 | 70 days | 8 | 12 | 3 |
| Once weekly | 1 | 140 days | 4 | 16 | 4 |
Dose days are spread through the week (3× weekly falls on days 0, 2 and 4, like Monday, Wednesday and Friday). Doses on day 28 or later count as expired.
Worked examples
Example 1: 10 mg vial, 250 mcg daily
10,000 ÷ 250 = 40 doses, enough for 40 days. Daily doses fall on days 0 to 27 before a 28-day BUD, so 28 are usable and 12 doses (3 mg) expire. A vial of 7 mg or less would be finished in time, such as a 5 mg vial.
Example 2: 5 mg vial, 500 mcg three times a week
5,000 ÷ 500 = 10 doses. On a Monday, Wednesday, Friday pattern the last dose falls on day 21. With a 28-day BUD you finish 7 days early, with nothing wasted.
Example 3: 10 mg vial in 2 mL, 2.5 mg weekly, with 2 units of loss
Without loss the vial holds 4 weekly doses. The concentration is 5 mg/mL, so each unit holds 50 mcg and 2 lost units are 100 mcg per injection. Each injection now uses 2.6 mg, and the vial gives only 3 full doses, leaving 2.2 mg that is not a full dose.
Example 4: a label with a 14-day in-use period
Take a 5 mg vial at 250 mcg daily whose label allows 14 days after mixing. The vial holds 20 doses, but only 14 fall inside 14 days, so 6 doses (1.5 mg) expire. Enter 14 in the beyond-use field to see this.
Dead space and priming loss
Not every drop in a vial reaches you. Some liquid stays in the needle and hub after each injection, some is squirted out while removing air bubbles, and a little always clings to the vial and stopper. The amount depends on the syringe and your technique, so the calculator leaves it at zero unless you enter a value.
If you know you lose about 1 unit per injection, enter 1. The calculator converts units to mcg using the water volume, adds that to each dose and recounts the whole doses. The effect is small with daily doses of a few units and larger with big doses or long schedules. The loss in units depends on the concentration too, so check it with the peptide reconstitution calculator if you change the water volume. To see what a given number of units contains, use the reverse peptide calculator.
Planning refills and choosing a vial size
The calculator gives a Next vial needed date: the first scheduled dose that the current vial cannot cover, either because it is empty or because the BUD has passed. Plan the next vial for that day. Mixing it earlier starts its own 28-day clock early and wastes days of its window.
Example refill plan
The 5 mg vial from the timeline above was mixed on Sun, Sep 27. Its last dose falls on Fri, Oct 16, so the next vial is needed on Sat, Oct 17. Mixed that day, the new vial’s own beyond-use date is Sat, Nov 14, and the cycle repeats every 20 days. Put both dates on a calendar the day you mix, so the refill is never a surprise.
The table shows the largest vial you would use up within 28 days for common doses and frequencies. It is vial arithmetic only; it does not suggest a dose or a schedule.
| Dose | Daily | Every other day | 5× per week | 3× per week | 2× per week | Once weekly |
|---|---|---|---|---|---|---|
| 100 mcg | 2.8 | 1.4 | 2 | 1.2 | 0.8 | 0.4 |
| 250 mcg | 7 | 3.5 | 5 | 3 | 2 | 1 |
| 500 mcg | 14 | 7 | 10 | 6 | 4 | 2 |
| 1 mg | 28 | 14 | 20 | 12 | 8 | 4 |
| 2.5 mg | 70 | 35 | 50 | 30 | 20 | 10 |
Largest vial = doses before the BUD × dose. Without loss. A different label period changes every cell.
- Label every vial with the date mixed, the water volume and the BUD. Keep the BAC water volume the same between vials so your units stay the same.
- Re-check after any change. A new dose, frequency or water volume changes the dates. The peptide dosage calculator shows weekly totals and prints a units chart.
- Blends count once. For multi-peptide vials, use the component you dose by; the peptide blend calculator splits the amounts.
Common vial-life mistakes
- Starting the clock at the first dose. The BUD counts from first puncture, which is the day you add water.
- Counting partial doses. A leftover of 0.2 mg is not a 250 mcg dose.
- Treating 28 days as a minimum. It is a ceiling. Your label may allow fewer days.
- Using a sterile-water vial for days. Without a preservative, the label may require immediate use.
- Stretching doses to finish a vial. Changing your dose to beat a date is a clinical decision, not arithmetic.
- Mixing up units while planning. The FDA has reported dosing errors of 5 to 20 times the intended amount from confusion between mg, mL and units. Check every conversion with the mg to units calculator.
Key terms
- Beyond-use date (BUD)
- The date after which an opened or compounded preparation should not be used.
- Expiration date
- The manufacturer’s date for the sealed product. A BUD never goes past it.
- Multiple-dose vial
- A vial meant for several withdrawals, usually with a preservative.
- Single-dose vial
- A vial meant for one use, usually without a preservative.
- First puncture
- The first time a needle enters the stopper, including when you add water.
- Dead space
- Liquid left in the needle and hub after an injection.
- Lyophilized
- Freeze-dried powder, stored as labeled until you mix it.
Frequently asked questions
How many doses are in a peptide vial?
Divide the peptide in the vial by the dose and round down. A 5 mg vial holds 20 doses of 250 mcg, 10 doses of 500 mcg and 5 doses of 1 mg. The water volume changes the units per dose, not the number of doses. Loss to dead space lowers the count slightly. For the units in each dose, use the reconstitution calculator.
How many doses are in a 10 mg vial?
It depends only on the dose. A 10 mg vial holds 40 doses of 250 mcg, 20 doses of 500 mcg, 10 doses of 1 mg or 4 doses of 2.5 mg. Whether you can use them all depends on your schedule and the beyond-use date, which is what the calculator checks.
How long will my vial last?
Multiply the whole doses by the days between doses. 20 doses taken daily last 20 days; taken three times a week they last about 47 days. Then compare that with the beyond-use date. If the vial outlasts it, the extra doses cannot be used. The peptide dosage calculator shows the same supply math alongside weekly totals.
How long do peptides last in the fridge after mixing?
As long as the product label says, and no longer. The Humatrope label allows 28 days refrigerated at 2–8 °C; the Serostim 4 mg label allows 14 days when mixed with bacteriostatic water. Without a label period, USP <797> limits a punctured multiple-dose vial to 28 days.
What is the 28-day rule for multi-dose vials?
Once a multiple-dose vial is opened or needle-punctured, the CDC says to date it and discard it within 28 days unless the manufacturer states a different date. USP <797> sets the same 28-day limit. It never extends past the manufacturer’s expiration date.
Does the 28 days start when I mix the vial or at the first dose?
At first puncture. Injecting water into the vial punctures the stopper, so the clock starts on the day you mix, even if the first dose is later. That is why the calculator asks for the date mixed. Write that date on the vial label so you never have to guess it later.
Can I freeze reconstituted peptides to make them last longer?
Only if the label allows it. The Humatrope label, for example, says to avoid freezing the reconstituted cartridge. Freezing is not a way around the beyond-use date, which exists mainly because of contamination risk from repeated punctures. When a label says nothing about freezing, ask your pharmacist before trying it.
Is an unopened lyophilized vial subject to the 28 days?
No. The beyond-use clock starts at first puncture. An unopened powder vial follows the storage conditions and expiration date on its label. Keep it as labeled, often refrigerated and away from light, until you mix it. The reconstitution calculator helps you plan the water volume before that first puncture.
What should I do if my vial will expire before it runs out?
Plan around the date rather than stretching it. Ask your pharmacist or prescriber whether a smaller vial is available. The calculator shows the largest vial you would finish in time; the peptide dosage calculator shows the weekly totals behind that number.
Why does the calculator say fewer doses than I expected?
Three common reasons: it counts whole doses only, it subtracts any dead-space loss you entered, and it counts only the doses that fall before the beyond-use date. Open Show the math to see each step with your numbers. If you entered a loss in units, check the water volume too, because it sets how much peptide each lost unit contains.
Sources
We check every formula and figure on this page against primary sources. See our editorial policy for how we review content.
- USP General Chapter <797> Pharmaceutical Compounding: Sterile Preparations
- <797> FAQs (updated December 11, 2023)
- Preventing Unsafe Injection Practices
- HUMATROPE (somatropin) for injection: prescribing information
- SEROSTIM (somatropin) for injection: prescribing information
- FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products
Reviewed by the PeptideConvert Editorial Team
Last reviewed . PeptideConvert tools do arithmetic only. They do not recommend a dose, and nothing on this site is medical advice. Always follow the label and your prescriber. Read the full medical disclaimer.