Compounded semaglutide usually ships as a freeze-dried powder you reconstitute with bacteriostatic water.
Semaglutide reference doses are small (tenths of a milligram), so the concentration you pick has a big effect on readability.
More water lowers the concentration and spreads the same dose across more syringe units — easier to measure.
The total compound in the vial never changes; only units-per-draw change with the water volume.
A correctly mixed solution is clear; refrigerate it and track the reconstitution date.
Compounded semaglutide is typically supplied as a freeze-dried (lyophilized) powder that you reconstitute with bacteriostatic water before use. In plain terms: the method is identical to any peptide — the only semaglutide-specific wrinkle is that the doses are small, so the concentration you choose has a big effect on how readable the draw is.
Why the doses are small
Semaglutide is a long-acting GLP-1 receptor agonist. Its plasma half-life is roughly one week, which is what allows a once-weekly schedule and lets the drug build to a steady level over several doses1. Because it is so potent and long-lasting, the reference doses studied in trials are measured in tenths of a milligram — which is exactly why concentration matters so much here.
Concentration drives readability
At a high concentration, a small dose becomes a very small number of units — hard to measure accurately. Adding more water lowers the concentration and spreads the same dose across more units.
For a 5 mg vial and a 0.25 mg reference dose:
Water added
Concentration
0.25 mg draw (U-100)
1 mL
5 mg/mL
5 units
2 mL
2.5 mg/mL
10 units
3 mL
1.67 mg/mL
15 units
All three are the same total amount of compound and the same dose — only the units-per-draw differ. A draw around 10–25 units is generally the easiest to measure precisely.
The math
`` concentration = vial mg ÷ water mL units (U-100) = (dose mg ÷ concentration) × 100 ``
Handling notes
Room-temperature both items before mixing; add water down the vial wall; swirl, don't shake.
Use bacteriostatic water, whose preservative lets the vial be entered repeatedly2.
A properly reconstituted semaglutide solution is clear and colourless. Cloudiness or particles warrant a look at why a peptide turns cloudy.
Run your own vial size and water volume through the semaglutide calculator to see the exact units before you draw.
Try it with the calculator
CONCENTRATION
2.5 mg/mL
YOUR DRAW (U-100)
40 units
DOSES IN VIAL
5
0102030405060708090100
Frequently asked
How many units is a 0.25 mg semaglutide dose?
It depends entirely on the concentration you mix. If you reconstitute a 5 mg vial with 2 mL of water you get 2.5 mg/mL, and 0.25 mg is 0.1 mL = 10 units on a U-100 syringe. Change the water volume and the units change.
Why do compounded vials come lyophilized?
Freeze-dried peptide is far more stable in storage and shipping than a pre-mixed solution, because there is little water available for degradation reactions. Reconstitution is done by the end user, which is why the mixing math matters.
Why are semaglutide doses so small?
Semaglutide is a long-acting GLP-1 receptor agonist with a plasma half-life of about a week, so it accumulates to a steady level on a once-weekly schedule; the reference doses studied in trials are on the order of tenths of a milligram, not milligrams.
References
Overgaard RV, Delff PH, Petri KCC, Anderson TW, Flint A, Ingwersen SH. Population pharmacokinetics of semaglutide for type 2 diabetes.Diabetes Ther. 2019. DOI 10.1007/s13300-019-0581-y
Pfizer Injectables / U.S. Pharmacopeia Bacteriostatic Water for Injection, USP — prescribing information (0.9% benzyl alcohol added as a bacteriostatic preservative; multiple-dose container).DailyMed (U.S. National Library of Medicine). 2023. Bacteriostatic Water for Injection USP
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