Semaglutide Reconstitution 5mg: BAC Water & IU Chart

What Is a 5mg Semaglutide Vial?

A 5mg semaglutide vial is a small glass vial containing 5 milligrams of lyophilized (freeze-dried) semaglutide powder under vacuum. It is not ready to inject. Before any dose can be drawn, the powder has to be reconstituted with bacteriostatic water, which is sterile water containing 0.9% benzyl alcohol as an antimicrobial preservative. The preservative is what makes a multi-dose vial possible. Without it, the solution would only be safe for 24 hours.

The 5mg size is the most common entry-point vial in research-peptide and compounded-semaglutide contexts because it lines up well with early titration. At the starter 0.25mg dose, one 5mg vial covers about five months. At maintenance doses, it covers anywhere from a few weeks to about two weeks. The general semaglutide reconstitution guide covers all vial sizes and the full step-by-step technique. This page stays narrowly on the 5mg math.

Why the 5mg vial size in particular

FDA-approved semaglutide titration runs 0.25mg, then 0.5mg, then 1.0mg, then 1.7mg, then 2.4mg, escalating every four weeks per the Wegovy prescribing information. A 5mg vial covers the first three of those rungs comfortably and gives you margin while you assess tolerance. At the 2.4mg maintenance dose, a 5mg vial provides just over two injections, which is roughly two weeks of treatment. For the full clinical titration schedule, the semaglutide dosing guide covers the full protocol.

How Much BAC Water for a 5mg Semaglutide Vial?

There are two standard options when reconstituting a 5mg semaglutide vial. Both are used in published compounding protocols. Pick one, stick with it for the life of the vial, and label the vial accordingly. The difference is concentration, which then drives the IU value for every dose you draw.

The 5mg semaglutide reconstitution chart

This is the table to bookmark. It covers every weekly dose in the standard semaglutide protocol from the 0.25mg starter through the 2.4mg Wegovy maintenance dose, at both common reconstitution volumes.

The two standard 5mg reconstitution options at a glance, with IU values for the full semaglutide weekly dose ladder.

Which concentration should you choose?

For most users, 2mL is the better default. It keeps every injection volume in the table under 1mL, which means a single draw on a standard U-100 insulin syringe handles every dose from 0.25mg through 2.4mg without splitting. The 2.5mL option (2mg/mL) is mainly useful at the 0.25mg starter dose, where 12.5 IU is slightly easier to pull accurately on a 100-unit syringe than the 10 IU value at 2.5mg/mL. Some users prefer it for the first few weeks and then switch to 2mL on the next vial.

Do not go below 1mL of BAC water on a 5mg vial. Over-concentrating a peptide solution creates measurement error at low doses and is not standard practice in compounded protocols. If you are unsure which concentration to use, the semaglutide calculator shows the IU value for any combination of vial size, BAC water volume, and dose.

How Many Doses Does a 5mg Semaglutide Vial Provide?

Vial longevity is the other half of the question every searcher really has. Once you know the IU per dose, the next thing you want is how long the vial lasts at your current titration rung. The math is simple division: 5mg total peptide divided by the weekly dose. The table below covers the four standard rungs.

Doses per 5mg vial at each titration step

One practical note that does not show up in the math: a small residual, typically around 0.1mL, usually remains in the vial after the last draw. The figures above assume all 5mg is usable, which slightly overstates real-world yield. At 0.25mg the residual is rounding error; at 2.4mg it is the difference between two doses and almost two doses.

A note on syringe accuracy

At the 0.25mg starter dose, a 100-unit (1cc) insulin syringe carries more measurement error than necessary. Drawing 10 IU on a syringe marked in 2-unit increments is workable but not precise. A 0.5cc (50 IU) or 0.3cc (30 IU) insulin syringe makes early-titration doses noticeably easier to measure. Once you are at 0.5mg and above, a 1cc syringe is fine. The calculator displays the recommended syringe size alongside the IU value for any dose.

Step-by-Step: Reconstituting a 5mg Semaglutide Vial

This is the condensed 5mg-specific version. The general reconstitution guide walks through the full protocol with all vial sizes and edge cases. For a 5mg vial specifically, the workflow is short.

Supplies

• 5mg semaglutide vial (lyophilized white powder under vacuum)
• Bacteriostatic water (BAC water, 0.9% benzyl alcohol preservative)
• 1mL or 3mL syringe for measuring BAC water
• U-100 insulin syringe for dosing (0.3cc, 0.5cc, or 1cc depending on dose)
• Alcohol swabs
• Sharps container
• Refrigerator at 36 to 46°F (2 to 8°C)

The 5-step process

1. Draw the BAC water. Pull 2mL (or 2.5mL, depending on your chosen concentration) into a 3mL syringe. Pick one concentration and stay with it for the full life of this vial.
2. Wipe both vial tops. Use a fresh alcohol swab on the rubber septum of both the BAC water vial and the semaglutide vial. Let them air-dry for 10 to 15 seconds.
3. Inject the BAC water slowly down the inner vial wall. Insert the needle at about a 45-degree angle and aim the liquid stream at the inner glass surface, not directly onto the powder cake. Pushing water hard onto lyophilized peptide is a common cause of degradation.
4. Swirl gently. Never shake. Roll the vial between your palms in slow circles until the powder fully dissolves. The solution should look clear and colorless, sometimes with a faint yellow tint. Foaming, cloudiness, or visible particles means something went wrong.
5. Label and refrigerate. Write the reconstitution date on the vial. Store at 36 to 46°F (2 to 8°C). Do not freeze.

The angled-injection technique: water enters along the glass wall rather than blasting the powder cake directly.

Storage after reconstitution

• Refrigerate at 36 to 46°F (2 to 8°C). Do not freeze. Do not store in a medicine cabinet or on the counter.
• Use within 28 to 56 days. 28 days is the conservative beyond-use date for reconstituted peptides under USP General Chapter 797 reasoning. 56 days is what many compounding pharmacies cite based on semaglutide stability data.
• Discard if the solution turns cloudy, discolored, or develops particles. Visual inspection before each dose is standard practice.
• Label the vial with the reconstitution date. Two unlabeled vials in the same fridge is how mistakes happen.

Common Mistakes with 5mg Semaglutide Reconstitution

Most reconstitution problems trace back to one of six recurring errors. None of them are exotic; they show up regularly in user-community threads.

1. Using the wrong BAC water volume and not recalculating IU. The IU values in the chart only apply to the exact concentration you reconstituted at. Doing 2mL on one vial and 2.5mL on the next, and then continuing to use the same IU number, is a real failure mode.
2. Shaking the vial. Mechanical stress and air bubbles can degrade the peptide and cause foaming. Always swirl in slow circles.
3. Injecting BAC water directly onto the powder cake. Aim for the inner glass wall instead. Hitting the cake head-on is one of the most common preparation errors.
4. Storing at room temperature or in a medicine cabinet. Reconstituted semaglutide needs to live in the fridge for the entire shelf life. Room temperature exposure shortens stability significantly.
5. Substituting sterile water for BAC water. Sterile water has no preservative. A multi-dose vial reconstituted with sterile water is only safe for 24 hours, which defeats the entire point of a multi-week supply.
6. Confusing the reconstitution syringe with the dosing syringe. A 3mL syringe is for measuring the BAC water once, at reconstitution. A U-100 insulin syringe is for measuring the weekly dose. Swapping them gives you wildly wrong volumes.

Use the GLP3Planner Semaglutide Reconstitution Calculator

The chart above covers the standard 5mg scenarios. The free semaglutide calculator handles everything else: any vial size, any BAC water volume, any weekly dose, and the corresponding IU value on whichever syringe you are using. It also models the concentration curve over time given semaglutide's roughly 7-day half-life, which is useful when you are planning a titration, a step-down, or a temporary pause.

For the broader picture on dose scheduling, see the semaglutide dosing guide and the semaglutide dosage chart. Both walk through the four-week escalation schedule that the chart on this page is built around.