Semaglutide Calculator
A vial strength and a water volume give a concentration. A concentration and a syringe give units. Worked for the vial sizes tracked across vendors — not generic examples.
Last reviewed: September 20, 2026
Vial strength and water volume give a concentration; a dose then gives the unit mark it corresponds to.
For research purposes only. Always verify calculations independently before use.
On this page
What reconstitution is
Research-grade semaglutide ships from vendors as a lyophilized (freeze-dried) powder sealed in a vial. Reconstitution is the act of dissolving that powder in a liquid — typically bacteriostatic water — which turns a fixed mass of peptide (the vial’s labeled mg content) into a solution with a defined concentration, measurable in volume with a syringe. The mass doesn’t change; only how that mass is distributed through a volume of liquid changes.
Semaglutide itself is FDA-approved — as Ozempic, Wegovy, and Rybelsus, all sold as pre-filled, ready-to-use products that the patient never reconstitutes. None of those labels contain reconstitution instructions for that reason. The math below is generic pharmaceutical arithmetic (concentration = mass ÷ volume), applied to the vial sizes research-grade semaglutide is actually sold in. For the compound’s mechanism (a GLP-1 receptor agonist) and trial evidence, see the semaglutide profile.
What sizes does semaglutide come in?
Read from live price data on September 20, 2026 (non-retired vendors only), 25 distinct vendors carry semaglutide. Only five sizes are carried by 3 or more of those vendors, and coverage is heavily concentrated at the bottom of that range: 5 mg and 10 mg carry 14 and 20 vendors respectively, while 15 mg, 20 mg, and 30 mg sit at just 3–4 vendors each. That concentration reflects semaglutide’s own FDA-labeled doses, which top out under 2.5 mg per week — far lower than tirzepatide’s or retatrutide’s, which is why those compounds’ vendor rosters run to much larger, more evenly-spread vial sizes.
| Vial size | Vendors tracking this size |
|---|---|
| 5 mg | 14 |
| 10 mg | 20 |
| 15 mg | 3 |
| 20 mg | 4 |
| 30 mg | 4 |
The arithmetic, worked
Concentration (mg/mL) equals the vial’s total mg divided by the water volume in mL. Micrograms per syringe unit, on a U-100 syringe (100 units = 1 mL), equals that concentration multiplied by 10. The table below reports both figures at two illustrative water volumes for each tracked size — as a statement of what each volume does to the concentration, not a recommendation of either:
| Vial size | At 1 mL water | At 2 mL water |
|---|---|---|
| 5 mg | 5 mg/mL — 50 mcg/unit | 2.5 mg/mL — 25 mcg/unit |
| 10 mg | 10 mg/mL — 100 mcg/unit | 5 mg/mL — 50 mcg/unit |
| 15 mg | 15 mg/mL — 150 mcg/unit | 7.5 mg/mL — 75 mcg/unit |
| 20 mg | 20 mg/mL — 200 mcg/unit | 10 mg/mL — 100 mcg/unit |
| 30 mg | 30 mg/mL — 300 mcg/unit | 15 mg/mL — 150 mcg/unit |
Doubling the water volume halves the concentration and halves the mcg delivered per unit drawn. The general dosage calculator runs this same arithmetic for any vial size and water volume, including ones outside the table above.
Units to draw, by vial size and dose
Every cell is the U-100 unit mark a given dose comes to, for a given vial strength, at 2 mL of bacteriostatic water. The rows are the vial sizes three or more tracked vendors carry; the columns are round dose values, chosen so the table reads cleanly across that range. They are not a schedule and nothing here suggests one — the label schedules for the branded semaglutide products are set out in the Ozempic and Wegovy dosing guides.
| Vial | 0.25 mg | 0.5 mg | 1 mg | 2 mg | 3 mg | 5 mg |
|---|---|---|---|---|---|---|
| 5 mg | 10.0 | 20.0 | 40.0 | 80.0 | 120.0 | 200.0 |
| 10 mg | 5.0 | 10.0 | 20.0 | 40.0 | 60.0 | 100.0 |
| 15 mg | 3.3 | 6.7 | 13.3 | 26.7 | 40.0 | 66.7 |
| 20 mg | 2.5 | 5.0 | 10.0 | 20.0 | 30.0 | 50.0 |
| 30 mg | 1.7 | 3.3 | 6.7 | 13.3 | 20.0 | 33.3 |
Figures over 100 are shown in amber: they exceed a 1 mL U-100 barrel at this water volume, so that combination does not fit one syringe. More water lowers the concentration and raises the unit count; less water does the reverse. The calculator above works any vial, volume and dose, in either direction.
What one vial comes to
The three sizes the most tracked vendors carry, worked at 2 mL. “Doses per vial” is the vial’s total divided by the dose — how many times that amount is present in the vial, before any loss in handling.
10 mg vial at 2 mL — 5.00 mg/mL
| Dose | Units to draw | Draw volume | Doses per vial |
|---|---|---|---|
| 0.25 mg | 5.0 | 0.05 mL | 40.0 |
| 0.5 mg | 10.0 | 0.10 mL | 20.0 |
| 1 mg | 20.0 | 0.20 mL | 10.0 |
| 2 mg | 40.0 | 0.40 mL | 5.0 |
| 3 mg | 60.0 | 0.60 mL | 3.3 |
| 5 mg | 100.0 | 1.00 mL | 2.0 |
5 mg vial at 2 mL — 2.50 mg/mL
| Dose | Units to draw | Draw volume | Doses per vial |
|---|---|---|---|
| 0.25 mg | 10.0 | 0.10 mL | 20.0 |
| 0.5 mg | 20.0 | 0.20 mL | 10.0 |
| 1 mg | 40.0 | 0.40 mL | 5.0 |
| 2 mg | 80.0 | 0.80 mL | 2.5 |
| 3 mg | 120.0 | 1.20 mL | 1.7 |
| 5 mg | 200.0 | 2.00 mL | 1.0 |
20 mg vial at 2 mL — 10.00 mg/mL
| Dose | Units to draw | Draw volume | Doses per vial |
|---|---|---|---|
| 0.25 mg | 2.5 | 0.03 mL | 80.0 |
| 0.5 mg | 5.0 | 0.05 mL | 40.0 |
| 1 mg | 10.0 | 0.10 mL | 20.0 |
| 2 mg | 20.0 | 0.20 mL | 10.0 |
| 3 mg | 30.0 | 0.30 mL | 6.7 |
| 5 mg | 50.0 | 0.50 mL | 4.0 |
What changes the answer
- Water volume. Concentration is inversely proportional to water volume. A larger water volume produces a lower concentration, meaning more units are needed to reach the same mg amount. Because semaglutide’s FDA-labeled doses are the smallest of the three compounds on this site’s dosing guides (well under 1 mg per injection for most of the escalation schedule), a lower concentration is more likely here than with tirzepatide or retatrutide to produce a workably small unit count rather than an unworkably large one.
- Vial size. For a fixed water volume, concentration is directly proportional to vial size — a 10 mg vial reconstituted with 1 mL is twice the concentration of a 5 mg vial reconstituted the same way.
- Syringe calibration. Every figure above assumes a U-100 syringe (100 units = 1 mL), the standard for peptide research (see the syringes and injection guide). A different calibration would report a different units figure for the identical physical volume; it does not change the concentration or the mg delivered.
How long does reconstituted semaglutide last?
Wegovy’s label states its pre-filled single-dose pen or syringe is refrigerated at 2–8°C (36–46°F), and may be kept, prior to cap removal, at 8–30°C (46–86°F) for up to 28 days. That figure describes a manufactured, ready-to-use solution — not a research-grade lyophilized vial before or after a buyer reconstitutes it with bacteriostatic water.
Prof. Peptide has not identified a sourced figure for how long reconstituted research-grade semaglutide remains stable, refrigerated or otherwise, from any manufacturer, regulator, or published study. This page does not state one as fact. A vendor’s own product page may state a shelf-life figure; that is the vendor’s claim, not an independently verified one, and is outside what this page reports.
FAQ
How do I reconstitute semaglutide?
Does the water volume change how much semaglutide is in the vial?
Why are semaglutide vials smaller than tirzepatide or retatrutide vials?
What syringe do the unit figures on this page assume?
Is this the same as how Ozempic or Wegovy are dosed?
How much BAC water for a 5mg semaglutide vial?
How much BAC water for a 10mg semaglutide vial?
How much BAC water for a 15mg semaglutide vial?
How much BAC water for a 20mg semaglutide vial?
How much BAC water for a 30mg semaglutide vial?
References
- Novo Nordisk. WEGOVY (semaglutide) injection and tablets — prescribing information, section 16 (How Supplied/Storage and Handling). DailyMed, setid ee06186f-2aa3-4990-a760-757579d8f77b, effective 2026-06-18. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ee06186f-2aa3-4990-a760-757579d8f77b
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