How many mg is N units of semaglutide?
Short answer: it depends on your vial, and anyone giving you one fixed number for “10 units” or “20 units” is skipping a step. Here's why, two worked examples to make it concrete, and a calculator below that works out the real number for your specific vial.
Why there's no single “units to mg” conversion
A syringe unit is a measurement of volume, not drug quantity — on a standard U-100 insulin syringe, 100 units always equals 1 mL, full stop, regardless of what's dissolved in that mL. How many milligrams of semaglutide are in that mL depends entirely on the vial's concentration — the mg of drug per mL of fluid once it's reconstituted — and concentration is not a fixed number for semaglutide the way it is for, say, an FDA-approved Wegovy pen.
Wegovy ships as pre-filled single-dose pens and syringes at one fixed strength each (0.25 mg, 0.5 mg, 1 mg, 1.7 mg, 2.4 mg, or 7.2 mg — see the reference box on the main semaglutide calculator page for the sourcing) and needs no reconstitution at all. Compounded semaglutide doesn't work that way: it's typically sold as a multi-dose vial containing a stated mg total (say, 5 mg, 10 mg, or 20 mg of powder or lyophilized drug), which a pharmacy or the person using it then reconstitutes by adding a chosen volume of bacteriostatic water. A 5 mg vial mixed with 1 mL of diluent is twice as concentrated as the same 5 mg vial mixed with 2 mL — and “20 units” of the first vial delivers twice the semaglutide that “20 units” of the second one does. Neither vial size nor diluent volume is standardized across pharmacies, so a units-to-mg figure that doesn't name a concentration is, at best, a guess.
Two worked examples
These use round, clearly hypothetical numbers to show the arithmetic. They are examples of the math, not a claim about what your vial contains — use the calculator below with your own vial's actual numbers for a real answer.
Example A
Say a 5 mg vial is reconstituted with 2 mL of bacteriostatic water. That's a concentration of 5 mg ÷ 2 mL = 2.5 mg/mL. At that concentration, 20 units (0.2 mL) works out to 0.2 mL × 2.5 mg/mL = 0.5 mg.
Example B
Same 5 mg vial, but reconstituted with 1 mL instead. That's a concentration of 5 mg ÷ 1 mL = 5 mg/mL — twice as strong. At that concentration, the same 20 units (0.2 mL) works out to 0.2 mL × 5 mg/mL = 1 mg — double Example A's answer, from the identical syringe reading.
Same vial size, same syringe reading, different diluent volume — a 2× difference in the actual dose. That gap is the whole reason a generic “20 units = 0.5 mg” answer circulating online can be flatly wrong for a real vial.
Convert your actual vial
Enter your vial's labeled mg amount, how much diluent you (or your pharmacy) added, and the dose your prescriber told you to take — the calculator works out your real concentration, draw volume, and syringe reading.
Semaglutide reconstitution
Fill in all three fields to see exactly where the plunger lands.
Not sure what your vial's mg or mL are?
Check the vial's label or your pharmacy's paperwork — the total mg is printed on the vial itself, and the diluent volume is whatever you (or the pharmacy) added when reconstituting it, not a number the vial states on its own. If either figure is unclear, ask your prescriber or pharmacist before drawing anything up; do not estimate it from a units figure you saw online.
Where to go next
- Use the full reconstitution tool with more reference context on the main semaglutide calculator.
- See how the providers selling compounded semaglutide compare on our semaglutide provider board.
- Read about compounded semaglutide's current legal status in our evidence article.
- See the FDA label's full titration ladder alongside this same mg/mL arithmetic on the semaglutide dosage chart.
Medical disclaimer: This content is for general educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a licensed healthcare professional before starting, stopping, or changing any treatment.