How much bacteriostatic water do you need for a 5 mg vial of Semaglutide?

That depends on the concentration you are working to, so it is arithmetic rather than a fixed number. 5 mg of Semaglutide in 1 mL of bacteriostatic water gives 5 mg/mL; in 2 mL it gives 2.5 mg/mL; in 5 mL it gives 1 mg/mL. Every volume on this page falls between 1 mL and 5 mL, so one 10 mL vial of bacteriostatic water covers this mix.

What concentration does 5 mg of Semaglutide in 2 mL give?

2.5 mg/mL. 5 mg ÷ 2 mL = 2.5 mg/mL. On a 1 mL U-100 insulin syringe that is 0.025 mg in each unit mark and 0.25 mg in ten marks.

How do you work this out yourself?

Divide the amount of powder printed on the vial by the number of millilitres of water added. The answer is the concentration, in mg per millilitre. To turn that into syringe marks, divide again by 100, because 100 unit marks on a U-100 insulin syringe is exactly 1 mL.

Does this page say what amount to use?

No. This page is dilution arithmetic. It says what is in the vial once powder and water are mixed, and nothing at all about what to do with it afterwards. That belongs to the prescriber or the researcher responsible for the vial.

Bacteriostatic water for 5 mg Semaglutide

Mixing a 5 mg vial of Semaglutide with 2 mL of bacteriostatic water gives a concentration of 2.5 mg/mL, which puts 0.25 mg in every 10 unit marks on a 1 mL U-100 insulin syringe.

Other water volumes give other concentrations. The full chart is below, with the arithmetic written out so you can check it against your own vial rather than taking this page at its word.

Bac water chart for 5 mg Semaglutide

Water volume, resulting concentration and syringe marks for a 5 mg vial of Semaglutide
Bacteriostatic water added	Resulting concentration	In 1 unit mark	In 10 unit marks	Whole vial, in unit marks
1 mL	5 mg/mL	0.05 mg	0.5 mg	100 units
2 mL	2.5 mg/mL	0.025 mg	0.25 mg	200 units
2.5 mL	2 mg/mL	0.02 mg	0.2 mg	250 units
3 mL	~1.6667 mg/mL	~0.0167 mg	~0.1667 mg	300 units
5 mL	1 mg/mL	0.01 mg	0.1 mg	500 units

Unit marks are the numbered lines on a 1 mL U-100 insulin syringe: 100 marks = 1 mL, so one mark is 0.01 mL. A value written with a leading “~” has been rounded for display; amounts are shown in mg.

The arithmetic, shown

5 mg ÷ 2 mL = 2.5 mg/mL
2.5 mg/mL ÷ 100 unit marks per mL = 0.025 mg per unit mark

Concentration is the amount of powder divided by the volume of water. The volume of the powder itself is not counted, because at these amounts it is far smaller than the smallest line on the syringe - the same assumption every printed reconstitution chart makes.

What each mark holds at 2.5 mg/mL

At 2.5 mg/mL - that is 5 mg in 2 mL - a 1 mL U-100 insulin syringe reads like this. One unit mark is 0.01 mL, because 100 marks make 1 mL.

What each unit mark on a 1 mL U-100 insulin syringe holds at 2.5 mg/mL
Unit mark	Volume	Contains
2	0.02 mL	0.05 mg
4	0.04 mL	0.1 mg
5	0.05 mL	0.125 mg
10	0.1 mL	0.25 mg
15	0.15 mL	0.375 mg
20	0.2 mL	0.5 mg
25	0.25 mL	0.625 mg
30	0.3 mL	0.75 mg
40	0.4 mL	1 mg
50	0.5 mL	1.25 mg
60	0.6 mL	1.5 mg
80	0.8 mL	2 mg
100	1 mL	2.5 mg

How much bacteriostatic water do you need?

You need about 5 mL of bacteriostatic water to mix a 5 mg vial of Semaglutide.

Every water volume in these charts is between 1 mL and 5 mL, so a single 10 mL vial of bacteriostatic water covers the largest of them 2 times over. Bacteriostatic water is sterile water that contains 0.9% benzyl alcohol as a preservative, which is what allows the same vial to be punctured more than once.

See the 10 mL vial

Storage and shelf life

Bacteriostatic water is sterile water that contains 0.9% benzyl alcohol as a preservative. The preservative is the reason a vial can be entered more than once rather than being discarded after a single use. An unopened vial keeps until the expiry date printed on it; once the stopper has been punctured, the discard window printed in the manufacturer’s insert for that vial applies.

Store water and mixed vials as the labelling for each one directs, out of direct light. If the liquid changes colour, goes cloudy, or shows anything floating in it, it goes in the bin rather than in a syringe.

How long bacteriostatic water lasts, in detail

Common questions

How much bacteriostatic water do you need for a 5 mg vial of Semaglutide?: That depends on the concentration you are working to, so it is arithmetic rather than a fixed number. 5 mg of Semaglutide in 1 mL of bacteriostatic water gives 5 mg/mL; in 2 mL it gives 2.5 mg/mL; in 5 mL it gives 1 mg/mL. Every volume on this page falls between 1 mL and 5 mL, so one 10 mL vial of bacteriostatic water covers this mix.
What concentration does 5 mg of Semaglutide in 2 mL give?: 2.5 mg/mL. 5 mg ÷ 2 mL = 2.5 mg/mL. On a 1 mL U-100 insulin syringe that is 0.025 mg in each unit mark and 0.25 mg in ten marks.
How do you work this out yourself?: Divide the amount of powder printed on the vial by the number of millilitres of water added. The answer is the concentration, in mg per millilitre. To turn that into syringe marks, divide again by 100, because 100 unit marks on a U-100 insulin syringe is exactly 1 mL.
Does this page say what amount to use?: No. This page is dilution arithmetic. It says what is in the vial once powder and water are mixed, and nothing at all about what to do with it afterwards. That belongs to the prescriber or the researcher responsible for the vial.

Semaglutide is a prescription medication that some compounding pharmacies supply as a freeze-dried powder, to be mixed with a liquid before use. It is available on prescription only. This site sells bacteriostatic water. It does not sell Semaglutide.

Ozempic and Wegovy are registered trademarks of their respective owners. This site is not affiliated with, endorsed by or sponsored by them, and does not supply Semaglutide in any form. The brand names appear here only because they are what people search for.