How do you reconstitute semaglutide?

Add 1–2 mL of bacteriostatic water to a 5 mg vial of semaglutide. Using 1 mL gives a concentration of 5 mg/mL; using 2 mL gives 2.5 mg/mL. Most research protocols use 1 mL for a clean, concentrated solution. Swirl gently until dissolved - never shake. Refrigerate and use within 28 days.

How many units is 0.25 mg of semaglutide on an insulin syringe?

At a concentration of 5 mg/mL (1 mL bacteriostatic water in a 5 mg vial), a 0.25 mg dose = 5 units on a U-100 insulin syringe. At 2.5 mg/mL (2 mL water), the same 0.25 mg dose = 10 units.

FAQ

How to reconstitute semaglutide

Semaglutide is a GLP-1 receptor agonist with a long plasma half-life of approximately 7 days, enabling once-weekly dosing in research protocols. It is supplied as a lyophilized white powder and must be dissolved in bacteriostatic water before use. The reconstitution process is identical in principle to other peptides, but semaglutide's molecular weight and structure require careful handling to preserve its fatty acid chain - responsible for its extended half-life.

TL;DR - Add 1–2 mL bacteriostatic water to a 5 mg vial. 1 mL = 5 mg/mL (most common); 2 mL = 2.5 mg/mL. Swirl gently to dissolve. Mark the date, refrigerate, and use within 28 days.

Step-by-step reconstitution

Allow the semaglutide vial to come to room temperature for 10–15 minutes if it was refrigerated. This reduces the chance of incomplete dissolution and minimizes the thermal shock to the peptide when water is added.

Wipe the rubber stopper of both the semaglutide vial and the bacteriostatic water vial with a fresh alcohol swab. Allow to air-dry for 10 seconds.

Draw your chosen volume of bacteriostatic water into the syringe. For a 5 mg vial, 1 mL is the standard (5 mg/mL). Use 2 mL if you prefer larger volume draws for lower doses.

Insert the needle so it points at the inner glass wall - not at the powder. Slowly push the plunger so water trickles down the wall and gently wets the powder from beneath. This minimizes foaming and shear stress.

Remove the needle and gently roll the vial between your palms with slow circular motions. Do not shake. Semaglutide typically dissolves within 30–60 seconds of gentle rolling. The solution should be completely clear.

Write the reconstitution date on the vial label with a permanent marker. Place in the refrigerator immediately at 2–8°C.

Concentration table (5 mg vial)

Water Added	Concentration	0.25 mg dose =	0.5 mg dose =
1 mL	5 mg/mL	5 units	10 units
2 mL	2.5 mg/mL	10 units	20 units
3 mL	1.67 mg/mL	15 units	30 units

The highlighted row (1 mL) is the most common protocol. It produces smaller draw volumes, which some researchers find easier to measure precisely on a U-100 syringe.

Starting dose context

In research literature mirroring clinical GLP-1 titration schedules, semaglutide is typically introduced at a low weekly dose of 0.25 mg to establish tolerance before escalation. At a concentration of 5 mg/mL (1 mL water in a 5 mg vial), this corresponds to drawing to exactly 5 units on a U-100 insulin syringe - a very small, precise volume.

Subsequent dose escalation steps commonly move through 0.5 mg, 1.0 mg, and 2.0 mg weekly doses, corresponding to 10, 20, and 40 units respectively at the same 5 mg/mL concentration. A single 5 mg vial provides 20 doses at the starting 0.25 mg level, or 10 doses at 0.5 mg.

Semaglutide's plasma half-life of approximately 165–184 hours (about 7 days) is the property that enables once-weekly dosing. This extended half-life is conferred by a C18 fatty diacid chain attached at lysine-26, which enables reversible binding to albumin and reduces renal clearance. This structural feature also makes semaglutide somewhat more sensitive to physical denaturation than smaller linear peptides.

Storage after reconstitution

Refrigerate at 2–8°C immediately after reconstitution. The benzyl alcohol preservative in bacteriostatic water provides antimicrobial protection but does not halt peptide degradation. Use within 28 days of reconstitution.

Keep the vial away from light. Amber vials or foil wrapping are ideal. Do not store near the refrigerator door where temperature fluctuates with opening and closing. The back shelf of the refrigerator maintains the most stable temperature.

Never freeze reconstituted semaglutide. Ice crystal formation disrupts the fatty acid chain's albumin-binding domain and aggregates the peptide. Freeze-thaw damage is irreversible and results in loss of potency without visible change in the solution's appearance.

Tip: Mark the reconstitution date on the vial as soon as you add the water - not the next day, not "later." The 28-day stability clock starts immediately. Use ASCEND's calculator to confirm your exact draw-to-unit markings for each dose escalation step.

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Research References

Wilding JPH et al. - Once-Weekly Semaglutide in Overweight/Obesity (STEP 1)
NEJM 2021 · PMID 33567185 · NCT03548935

Marso SP et al. - Semaglutide and Cardiovascular Outcomes (SUSTAIN-6)
NEJM 2016 · PMID 27633186 · NCT01720446

ASCEND is a mathematical reference tool for research purposes only. Not for medical use.
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