Educational reference only — not medical advice. This calculator does maths only and does not recommend any dose. Always confirm your dose and preparation with a licensed healthcare provider or pharmacist.
Reconstitution Calculator
Results update live as you type. Your dose must come from your prescription or provider — this tool never suggests one.
Printed on the vial label — the total powder in the vial.
The volume of bacteriostatic water you mix into the vial.
Enter the dose exactly as given to you. 1 mg = 1,000 mcg.
U-100 syringes: 100 units = 1 mL, whatever the barrel size.
Nothing you type leaves this page — the calculation runs entirely in your browser. Educational reference only, not medical advice.
Semaglutide is the odd one out on this site. Most peptides here are research chemicals; semaglutide is a real, FDA-approved prescription medicine — and the version most people know, the pen, has nothing to do with this calculator. This page is only for the powder vials. If yours is a pen, stop here: the maths does not apply to it.
What is Semaglutide?
Semaglutide is a long-acting GLP-1 receptor agonist, a peptide analogue of the human gut hormone GLP-1 (about 94% sequence homology to native GLP-1). It is made by Novo Nordisk and sold as Ozempic, Wegovy and Rybelsus. Ozempic was approved in December 2017 for type 2 diabetes, Rybelsus — the oral tablet — in September 2019, and Wegovy in June 2021 for chronic weight management. It is prescription-only everywhere it is approved.
Pens and tablets vs powder vials — read this first.
The approved products come as pre-filled pen injectors containing solution, or as oral tablets. There is nothing to reconstitute: a pen delivers a set amount exactly as your prescriber instructed. The calculator on this page is only for lyophilised semaglutide powder in vials, which comes from compounding and research supply. Do not mix the two systems up. The branded pen strengths (Wegovy 0.25, 0.5, 1, 1.7 and 2.4 mg per injection; Ozempic pens delivering 0.25/0.5, 1 or 2 mg) are pen doses, not vial sizes — they do not belong in this calculator.
The vial maths.
Powder vials are most commonly sold as 3 mg, 5 mg and 10 mg. There is no single correct water volume; sources commonly discuss 1–3 mL per vial.
Worked example — 5 mg vial, 2 mL of BAC water, example dose 250 mcg:
- Concentration: (5 × 1,000) ÷ 2 = 2,500 mcg/mL
- Each unit holds 2,500 ÷ 100 = 25 mcg
- Units for the example dose: 250 ÷ 25 = 10 units (0.1 mL)
- Doses in the vial: 5,000 ÷ 250 = 20 doses
A 3 mg vial in 2 mL gives 1,500 mcg/mL instead, so the same example dose would take about 17 units. The vial size and the water volume both matter — the calculator takes both.
Storage (commonly cited):
Lyophilised powder at −20 °C for long-term storage, 2–8 °C for short periods. Once mixed, refrigerate at 2–8 °C, protect from light, do not freeze. The usable window is disputed in sources (~7–14 days in one, ~28 days in others); treat ~28 days as a commonly cited planning figure, not a settled fact, and follow your product’s own label.
FAQs
My semaglutide is a pre-filled pen. Do I need this calculator?
No. Approved pens are pre-mixed and dose in set amounts exactly as your prescriber instructed — follow the pen instructions and your prescription. This page is only for powder vials you mix with BAC water yourself.
How many units is my dose from a 5 mg semaglutide vial?
With 2 mL of water, a 5 mg vial gives 2,500 mcg/mL, so each unit contains 25 mcg: units = your dose in mcg ÷ 25. If your dose is written in mg, multiply it by 1,000 first (or use the mg toggle).
Why do semaglutide vials come in different sizes?
Vial size is simply how much powder the supplier put in. Concentration depends on both the labelled mg and the water you add, so a 10 mg vial in 2 mL is twice as strong per unit as a 5 mg vial in 2 mL. Always calculate from your own label.
Is semaglutide FDA-approved?
Yes — as Ozempic, Wegovy and Rybelsus, prescription-only. That approval covers the branded products, not research-chemical powder vials.
Related calculators
See also the Tirzepatide Calculator and the Peptide Calculator home page.
Educational reference only — not medical advice. This calculator does maths only and does not recommend any dose. Always confirm your dose and preparation with a licensed healthcare provider or pharmacist.