Reconstitution Guide
How to reconstitute compounded Semaglutide — exact measurements
Compounded Semaglutide comes as a lyophilized powder. You add bacteriostatic water to create a liquid solution at a specific concentration. How much water you add determines how many units you draw per dose. Getting the math wrong means you are either underdosing or taking more than prescribed.
Updated August 2026 · 6 min read
What you need
Compounded Semaglutide vial
Lyophilized powder, typically 2.5mg, 5mg, or 10mg per vial
Bacteriostatic water (BAC water)
Not saline. Not sterile water. BAC water has benzyl alcohol preservative.
Two syringes
One to transfer the BAC water, one for injections. Standard U-100 insulin syringes work for drawing.
Alcohol swabs
Wipe the rubber stopper of each vial before each puncture
Refrigerator space
Reconstituted Semaglutide must be refrigerated at 36-46°F immediately after mixing
The reconstitution steps
Calculate how much BAC water to add
This is the step most people skip or guess on. The amount of BAC water you add determines the concentration of your solution, which determines how many units you draw per dose. See the reference table below or use Protocol's reconstitution calculator to get the exact volume for your vial size and dose.
Wipe both vials with an alcohol swab
Swab the rubber stopper on both the Semaglutide vial and the BAC water vial. Let dry for 10-15 seconds. This is not optional — it prevents contamination that degrades the compound and creates infection risk.
Draw the BAC water
Using a clean syringe, draw the calculated volume of BAC water from its vial. For a 5mg Semaglutide vial reconstituted to 2.5mg/mL, draw 2mL of BAC water.
Inject BAC water into the Semaglutide vial slowly
Angle the needle so the stream runs down the inside wall of the vial rather than hitting the powder directly. Semaglutide is a peptide and the protein structure can denature from mechanical agitation. Do not shake the vial. A gentle swirl or slow inversion is sufficient to mix.
Wait and verify
The powder should dissolve within a minute. The solution should be clear and colorless. Slight yellow tinting is normal for some formulations. Cloudiness, visible particles, or a noticeably colored solution are signs of degradation or contamination — do not use.
Refrigerate immediately
Label the vial with the date of reconstitution. Store at 36-46°F (2-8°C). Use within 28 days (or per your pharmacy's specific guidance). Never freeze.
Dose reference table — 5mg vial
All values assume a standard U-100 insulin syringe. Units = marks on the syringe.
5mg vial + 2mL BAC water
2.5mg/mL (2,500mcg/mL)
5mg vial + 1mL BAC water
5mg/mL (5,000mcg/mL)
Calculate your exact dose
Protocol's reconstitution calculator handles any vial size and dose combination. Works offline. No account required.
Open calculator →The most common mistakes
✗ Using sterile water instead of bacteriostatic water
Sterile water has no preservative. After the first puncture, it becomes a contamination risk. BAC water's benzyl alcohol keeps multi-dose vials safe for 28+ days.
✗ Adding too much BAC water to make the math simpler
Diluting more than necessary is fine for the math but means larger injection volumes per dose. Some users find this increases injection site discomfort. Pick a concentration your dose volumes make sense at.
✗ Shaking the vial to mix
Semaglutide is a peptide. Mechanical agitation can denature the protein. Swirl gently or invert slowly. The powder dissolves on its own within a minute.
✗ Not labeling the reconstitution date
Reconstituted Semaglutide looks the same at day 1 and day 35. Label the vial when you mix it so you know when it expires. Protocol's vial tracker does this automatically.
✗ Leaving it at room temperature
Refrigerate within minutes of reconstituting. Room-temperature Semaglutide degrades faster. Refrigerated and used within 28 days maintains potency.
Track vials and doses in Protocol
Log your reconstitution date, track doses remaining, and get expiry alerts. The reconstitution calculator is built into the app. Free on iOS and Android.
Frequently asked questions
How much bacteriostatic water do I add to compounded Semaglutide?+
The amount depends on your vial size and your target dose. A 5mg vial with 2mL of bacteriostatic water gives a concentration of 2.5mg/mL. At that concentration, a 0.25mg starting dose is 0.1mL — 10 units on a standard U-100 insulin syringe. A 0.5mg dose is 0.2mL (20 units). Protocol's free reconstitution calculator handles this math for any vial size and dose combination.
What is bacteriostatic water and where do I get it?+
Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol, which prevents bacterial growth and allows the vial to be multi-dose. It is available from research chemical suppliers, compounding pharmacies, and some online medical supply retailers. Do not substitute sterile water or saline — sterile water has no preservative and becomes a contamination risk after the first puncture. Saline can affect some peptide formulations.
How long does reconstituted Semaglutide last?+
Reconstituted compounded Semaglutide should be refrigerated at 36-46°F (2-8°C) and used within 28 days of mixing, per typical compounding pharmacy guidelines. Some formulations specify 30 or 56 days — check your pharmacy's documentation. Do not freeze reconstituted Semaglutide. Freezing denatures the protein structure and reduces potency. Protocol's vial tracker logs your reconstitution date and flags vials approaching expiry.
What is the difference between Semaglutide base and Semaglutide sodium?+
Semaglutide base is the free acid form. Semaglutide sodium is a sodium salt of Semaglutide. They have the same active compound but slightly different potency per milligram due to the weight of the sodium salt molecule. Reconstitution math and dosing are identical in practice for clinical purposes, but compounding pharmacies formulate using one or the other. Protocol's reconstitution calculator covers both forms.
Can I use Protocol's reconstitution calculator for Tirzepatide?+
Yes. Protocol's reconstitution calculator covers Tirzepatide, Semaglutide (base and sodium), Retatrutide, Liraglutide, and 77 additional compounds. The web version at protocolapp.health/tools/reconstitution-calculator is free and does not require downloading the app or creating an account.