How much bacteriostatic water do I add to a semaglutide vial?

Use the volume in your product's instructions or from your prescriber or pharmacist. The water doesn't change how much semaglutide is in the vial, only the concentration: a 5 mg vial with 2 mL is 2.5 mg/mL, and adding more water makes each unit on the syringe hold less.

How do I convert semaglutide from mg to syringe units?

Divide the amount in mg by the concentration in mg/mL to get mL, then multiply by 100 for a U-100 insulin syringe (50 for U-50, 40 for U-40). The calculator on this page does it when you enter the amount from your prescriber or label.

Does this calculator give a semaglutide dose?

No. The calculator's amount field starts empty and Caliper never suggests an amount. For reference, this page quotes the dosing section of the FDA label for Wegovy and Ozempic, which applies only to that branded product. Your dose comes from your prescriber.

How should I store semaglutide after mixing?

Follow the storage section of your product's label or the pharmacy's instructions. The notes on this page summarize what the FDA label says for the branded product. For any mixed vial, write the mixing date on it and respect the use-by date.

Do Wegovy or Ozempic need to be reconstituted?

No. Both come as ready-to-use solutions in pens or prefilled syringes, with the strength set by the device. Reconstitution math applies to powder vials, which are compounded or research products, not the FDA-approved brands.

Semaglutide reconstitution calculator

Concentration and syringe-unit math for semaglutide vials (2, 5 and 10 mg), with the calculator set up for a 5 mg vial and 2 mL of diluent. Change both to match your own vial.

FDA-approved product existsGLP-1 and incretin compounds

Semaglutide is a GLP-1 receptor agonist. The FDA-approved injectable brands are Wegovy (weight reduction and cardiovascular risk reduction) and Ozempic (type 2 diabetes); both come as ready-to-use solutions in pens or prefilled syringes, so there is nothing to reconstitute.

FDA-approved product: Wegovy and Ozempic. The official label dosing for the branded product is quoted further down this page for reference. It applies only to that product, and it is never filled into the calculator. Products sold for “research use only” are not the approved drug.

Reconstitution calculator

Enter the numbers from your own vial, and pick the syringe in your hand. Check the U- number and size printed on the syringe box.

Concentration

2.5 mg/mL

2,500 mcg/mL

Draw volume

—

Syringe units

—

U-100 1 mL, holds 100

Draws in the vial

—

1Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL
2Draw volume: amount in mg ÷ 2.5 mg/mL = draw mL
3Syringe units: draw mL × 100 units per mL (U-100) = units

Math only, not dosing advice. Follow your prescriber or label. Real vials give slightly less than the full-draw count: a little liquid stays in the vial and needle. Your last setup is saved in this browser only; Clear removes it.

Save your vial in Caliper and it remembers the concentration and use-by date you entered, alongside your dose log. The calculator above is a browser tool and is not part of the app.

Save my vial in Caliper

The calculator starts with a 5 mg vial and 2 mL of diluent as an example setup, not a recommendation. Enter the vial size on your label and the volume you actually added. The amount field starts empty: Caliper never suggests an amount.

Semaglutide concentration by vial size

Vial mg ÷ mL of diluent = mg per mL. Plain arithmetic for semaglutide label sizes; the volumes are examples, not recommendations.

Semaglutide: mg/mL by vial size and diluent volume
Vial	1 mL	2 mL	3 mL
2 mg	2 mg/mL	1 mg/mL	0.667 mg/mL
5 mg	5 mg/mL	2.5 mg/mL	1.667 mg/mL
10 mg	10 mg/mL	5 mg/mL	3.333 mg/mL

Syringe units to mg at 2.5 mg/mL

What a given number of U-100 units holds when a 5 mg vial has 2 mL added. This is a unit conversion, like a map scale, not a dose. A different vial size or volume changes every row, so use the calculator for your own numbers.

5 mg vial + 2 mL (2.5 mg/mL): conversion only
U-100 units	mL	mg	mcg
5 units	0.05	0.125	125
10 units	0.1	0.25	250
20 units	0.2	0.5	500
25 units	0.25	0.625	625
50 units	0.5	1.25	1,250

Mixing and storing semaglutide

This calculator is for powder vials and for any vial where you draw with an insulin syringe. A 5 mg vial with 2 mL added is 2.5 mg/mL; the same vial with 1 mL is 5 mg/mL. Whatever volume you add, the amount of semaglutide in the vial doesn't change, only the number of units per draw.

Wegovy single-dose pens and syringes are labeled for refrigeration at 2°C to 8°C (36°F to 46°F), and the label allows up to 28 days at 8°C to 30°C (46°F to 86°F) before the cap is removed. Don't freeze it, and don't use it if it has been frozen.

For compounded multi-dose vials, the FDA's guidance is to discard the vial within 28 days of first use, even if medicine is left and even if the instructions say longer.

Status: FDA-approved as Wegovy and Ozempic (and as tablets). Powder vials labeled semaglutide are compounded or research products, not the FDA-approved drug, and the FDA has said compounded drugs are not reviewed for safety, effectiveness or quality before they are marketed.

More detail: how to reconstitute peptides and how to store peptides and GLP-1s. To convert units you've already drawn, use the units-to-mg converter.

Official FDA label dosing for Wegovy and Ozempic

Follow your prescriber's instructions. This is not medical advice. The text below is quoted exactly from the current FDA prescribing information (section cross-references removed). It is the official label schedule for the branded product named and does not apply to compounded or research products. Labels change; the linked label is the authority.

WEGOVY injection: label schedule

Indication (from the label): “WEGOVY injection is indicated in combination with a reduced calorie diet and increased physical activity … to reduce excess body weight and maintain weight reduction long term in … adults and pediatric patients aged 12 years and older with obesity.”

“The recommended starting dosage of WEGOVY injection is 0.25 mg administered subcutaneously once weekly.”
“Follow the dosage escalation in Table 1 to reduce the risk of gastrointestinal adverse reactions.”
“If patients do not tolerate a dose during dosage escalation, consider delaying dosage escalation for 4 weeks.”
“The maintenance dosage of WEGOVY for weight reduction in adults is either 1.7 mg or 2.4 mg (recommended) injected subcutaneously once weekly.”
“For patients who tolerate the 2.4 mg dosage for at least 4 weeks and additional weight reduction is clinically indicated, the dosage may be increased to a maximum dosage of 7.2 mg subcutaneously once weekly.”

Table 1. Recommended Starting Dosage and Dosage Escalation of WEGOVY Injection for All Approved Indications in Adults and Pediatric Patients Aged 12 Years and Older
	Weeks	Once-weekly Subcutaneous Injection Dosage
Starting Dosage	1 through 4	0.25 mg
Dosage Escalation	5 through 8	0.5 mg
	9 through 12	1 mg
	13 through 16	1.7 mg
Maintenance Dosage	17 and onward	See the indication below for the recommended maintenance dosage(s)

Source: WEGOVY (semaglutide) prescribing information, DailyMed, label version effective June 18, 2026; checked October 17, 2026.

OZEMPIC injection: label schedule

Indication (from the label): “OZEMPIC is indicated: as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus.”

“Start at 0.25 mg once weekly. After 4 weeks, increase the dosage to 0.5 mg once weekly.”
“If additional glycemic control is needed, increase the dosage to 1 mg once weekly after at least 4 weeks on the 0.5 mg dose.”
“If additional glycemic control is needed, increase the dosage to 2 mg once weekly after at least 4 weeks on the 1 mg dosage.”
“The maximum recommended dosage is 2 mg once weekly.”

Source: OZEMPIC (semaglutide) injection prescribing information, DailyMed, label version effective June 1, 2026; checked October 17, 2026.

FAQ

How much bacteriostatic water do I add to a semaglutide vial?: Use the volume in your product's instructions or from your prescriber or pharmacist. The water doesn't change how much semaglutide is in the vial, only the concentration: a 5 mg vial with 2 mL is 2.5 mg/mL, and adding more water makes each unit on the syringe hold less.
How do I convert semaglutide from mg to syringe units?: Divide the amount in mg by the concentration in mg/mL to get mL, then multiply by 100 for a U-100 insulin syringe (50 for U-50, 40 for U-40). The calculator on this page does it when you enter the amount from your prescriber or label.
Does this calculator give a semaglutide dose?: No. The calculator's amount field starts empty and Caliper never suggests an amount. For reference, this page quotes the dosing section of the FDA label for Wegovy and Ozempic, which applies only to that branded product. Your dose comes from your prescriber.
Is semaglutide FDA-approved?: FDA-approved as Wegovy and Ozempic (and as tablets). Powder vials labeled semaglutide are compounded or research products, not the FDA-approved drug, and the FDA has said compounded drugs are not reviewed for safety, effectiveness or quality before they are marketed.
How should I store semaglutide after mixing?: Follow the storage section of your product's label or the pharmacy's instructions. The notes on this page summarize what the FDA label says for the branded product. For any mixed vial, write the mixing date on it and respect the use-by date.
Do Wegovy or Ozempic need to be reconstituted?: No. Both come as ready-to-use solutions in pens or prefilled syringes, with the strength set by the device. Reconstitution math applies to powder vials, which are compounded or research products, not the FDA-approved brands.

Related compounds

Calculators by vial size

The same arithmetic for any compound, with a 1, 2 and 3 mL concentration table.

Related guides

Sources

Updated October 17, 2026

For adults 18+. Educational math only, not medical advice. This page does not recommend any dose, dilution, syringe or compound, and doesn't say where to get one. Always follow your prescriber's instructions and the product label, and ask a pharmacist if a number doesn't look right.