How to Reconstitute Semaglutide: Mixing Guide and Units Chart

Semaglutide doses are tiny. We're talking fractions of a milligram, measured out as a handful of units on an insulin syringe. That's exactly why getting the reconstitution right matters so much. With a drug this concentrated, the difference between the right amount and a very wrong amount can be a single misread line on the syringe.

If you've been prescribed compounded semaglutide in a vial of powder, this guide walks you through how to mix it, how to work out what your vial's concentration is, and how to turn your prescribed dose into units. It won't tell you what dose to take. That part belongs to your prescriber. What it will do is make sure the number on your prescription and the number on your syringe actually agree.

Ozempic, Wegovy, and Rybelsus Never Need Mixing

Let's clear this up first, because a lot of confusion starts here. The FDA-approved semaglutide products don't need reconstitution.

Ozempic (for type 2 diabetes) comes in prefilled pens that are already a liquid solution, and in single-dose prefilled syringes, according to the Ozempic label on DailyMed. Wegovy (for weight management and cardiovascular risk reduction) comes as single-dose pens, single-dose syringes, a multi-dose FlexTouch pen, and tablets, per the Wegovy label on DailyMed. Rybelsus is an oral semaglutide tablet. None of these involve powder, diluent, or math. Follow the instructions that came with them.

This guide is only for compounded semaglutide supplied as a lyophilized (freeze-dried) powder. Here's the context you need about that.

Compounded drugs are not FDA-approved, and the FDA notes they aren't reviewed for safety, effectiveness, or quality before they reach you (FDA's concerns with unapproved GLP-1 drugs). The FDA declared the semaglutide shortage resolved on February 21, 2025, and the grace periods that let pharmacies make copies during the shortage ended in April and May 2025 (FDA policy update). A licensed pharmacy can still compound for an individual patient in limited circumstances, but mass-produced copies aren't allowed.

Two more red flags the FDA calls out. First, "semaglutide sodium" and "semaglutide acetate" are salt forms, which the FDA says are different active ingredients from the approved drug, with no lawful basis for compounding. Second, the FDA has warned companies selling semaglutide labelled "for research use only" or "not for human consumption." If your product is described either way, don't use it. Get semaglutide through a licensed prescriber and a licensed pharmacy.

And one practical point: many compounded semaglutide vials arrive already in solution. If yours is a liquid, don't add anything. Only reconstitute a vial clearly labelled as powder, using the diluent and volume the pharmacy specifies.

What You'll Need

Before you start, gather your semaglutide vial, the diluent your pharmacy supplied or named (usually bacteriostatic water, which contains a small amount of benzyl alcohol as a preservative; see the DailyMed label), alcohol swabs, a sterile syringe for adding the diluent, U-100 insulin syringes for your doses, and a sharps container.

For semaglutide in particular, the size of your dosing syringe matters. Doses often come out to single-digit or low double-digit units. A 0.3 mL (30 unit) syringe usually has markings at every single unit, while a 1 mL syringe typically marks every two units. Smaller syringe, easier to read.

How to Reconstitute Semaglutide Step by Step

The whole process takes about five minutes. Read all the steps before you start.

Step 1: Set up clean. Wash your hands with soap and water and clear a clean, flat surface. If the vial's been refrigerated, let it sit for a few minutes to come closer to room temperature.

Step 2: Swab both stoppers. Pop the plastic caps off the semaglutide vial and the diluent. Wipe each rubber stopper with a fresh alcohol swab and let it dry fully before you puncture it.

Step 3: Draw your diluent. Pull air into the syringe equal to the volume on your pharmacy label, push that air into the diluent vial, turn it upside down, and draw the liquid out. Flick away any large bubbles.

Step 4: Add it slowly down the glass. Insert the needle into the semaglutide vial at an angle and let the diluent trickle down the inside wall. Go slowly. Blasting liquid straight onto the powder can cause foaming and isn't kind to a delicate peptide.

Step 5: Swirl, don't shake. Pull the needle out and gently swirl the vial, or roll it between your palms. Most semaglutide dissolves within a minute or two. If some powder sticks to the glass, give it a few minutes in the fridge and swirl again.

Step 6: Check it and label it. You're looking for a clear, colourless liquid with no floating particles. Write the concentration and today's date on the vial. You'll thank yourself every week you pick it up.

Semaglutide Reconstitution Chart

This chart shows, for common compounded vial sizes, what concentration you get with different diluent volumes, how many units on a U-100 insulin syringe hold 1 mg, and how much semaglutide sits in 10 units (0.1 mL).

To use it, find your vial and diluent volume, then multiply the "units per 1 mg" by the milligrams on your prescription. Because semaglutide doses are usually well under 1 mg, the answer will be a fraction of that column. The last column is handy as a quick check: 10 units is easy to see on any syringe.

You'll notice some rows show more than 100 units per 1 mg. That's fine. It just means a full 1 mg wouldn't fit in a single 1 mL syringe at that dilution. For the much smaller amounts typically prescribed, those dilutions give you more units to measure, which can actually make small doses easier to draw accurately.

At the other end, a 10mg vial mixed with 1 mL puts 0.1 mg in every unit, and only 10 units in a full milligram. When each tick mark holds that much, reading the syringe carefully matters even more. The right volume for your vial is whatever your pharmacy label says.

How Much Bacteriostatic Water to Mix With Semaglutide?

There isn't a single correct answer, and anyone giving you one without seeing your vial label is guessing. Use the volume your pharmacy or prescriber specified.

What the chart shows is that the water only changes how concentrated the solution is. It doesn't change how much semaglutide is in the vial. A 2mg vial with 1 mL is 2 mg/mL, but with 2 mL it's 1 mg/mL. A 5mg vial with 2 mL is 2.5 mg/mL, so 40 units equals 1 mg.

If your vial didn't come with instructions, call the pharmacy before mixing. They'd much rather answer that question than hear about a dosing error.

Worked Example: Turning Your Prescription Into Units

Here's one example so you can see how the numbers flow. The amount is just for demonstrating the math, not a recommendation.

If your prescriber told you 0.25 mg, and your 5mg vial was mixed with 2 mL of bacteriostatic water:

The concentration is 5 mg ÷ 2 mL = 2.5 mg/mL. To get 0.25 mg, you need 0.25 ÷ 2.5 = 0.1 mL. On a U-100 syringe, that's 10 units. From the chart, it's 40 units per mg × 0.25 mg = 10 units.

Now watch what happens with different water volumes for that same prescription. If the same 5mg vial had been mixed with 1 mL, the concentration would be 5 mg/mL and 0.25 mg would be 5 units. With 3 mL, it'd be 1.667 mg/mL and 15 units. Same dose, three different numbers on the syringe.

That's the heart of the problem. If you switch pharmacies or vial sizes and keep drawing the units you're used to, your actual dose can jump or drop without you noticing. The semaglutide calculator is a quick way to double-check yourself whenever anything about your vial changes.

Why Units Cause So Many Mistakes

The FDA has received reports of people taking 5 to 20 times their intended dose of compounded semaglutide. In some cases, people drew 50 units when they meant to take 5. The agency traced many of these errors to confusion between milligrams, millilitres, and units, and it recommends that patients receive a syringe suited to their dose and be shown how to measure it (FDA alert on dosing errors).

Here's the idea to lock in. Units on an insulin syringe measure volume, not drug. 10 units is always 0.1 mL, no matter what's in the vial. How much semaglutide those 10 units contain depends entirely on how the vial was mixed.

This also means you can't transfer numbers between a branded pen and a compounded vial. The Ozempic pens, for example, contain 0.68, 1.34, or 2.68 mg/mL depending on the pen, per the label. Your compounded vial has its own concentration. Always do the math from your vial's label.

Storing Semaglutide Before and After Mixing

For the branded products, the labels give clear rules. An Ozempic pen is kept in the fridge at 2 to 8°C (36 to 46°F) before first use. After first use, it can be kept for 56 days at room temperature (15 to 30°C) or in the fridge. Wegovy single-dose pens stay in the fridge, and if needed can be kept at 8 to 30°C for up to 28 days before the cap comes off. None of them should ever be frozen.

For compounded semaglutide, storage directions come from the pharmacy. Before mixing, follow the label on the vial. After mixing, store it in the fridge, upright, away from light, and never frozen.

How long does it last once mixed? Look for a "beyond-use date" on the pharmacy label and follow it. Without one, the general CDC injection safety guidance for preserved multi-dose vials is to discard them 28 days after the first puncture, unless the manufacturer or pharmacy says otherwise.

Clear, Cloudy, or Bubbly?

Reconstituted semaglutide should be clear and colourless. If it looks cloudy, hazy, discoloured, or has specks in it, don't inject it. Contact the pharmacy. Foam or small bubbles on top right after mixing are usually air from adding the diluent too fast. Let the vial rest upright in the fridge. If it stays hazy once the bubbles are gone, treat it as cloudy.

Staying Consistent Week to Week

Weekly injections have a sneaky problem: seven days is just long enough to forget exactly what you did last time. Which day was it? How many units? Is this still the same vial?

PeptideKit keeps all of that in one place. You can set up a weekly semaglutide schedule, get a reminder on injection day, and use the built-in reconstitution calculator so your units always match the vial you mixed. You can also log how you're feeling, which makes conversations with your prescriber about side effects and titration much more concrete. If nausea or other GI effects are part of your week, our guide to managing GLP-1 side effects is worth a read.

Frequently Asked Questions

How do you reconstitute semaglutide?

Swab the stoppers, draw the diluent volume your pharmacy specified, and inject it slowly down the inside wall of the semaglutide vial. Gently swirl until the powder dissolves into a clear solution, without shaking. Label the vial with the concentration and date and keep it in the fridge. Ozempic, Wegovy, and Rybelsus never need reconstitution.

How much bacteriostatic water do I mix with semaglutide?

Use the volume on your pharmacy label. The water changes the concentration, not the amount of semaglutide. For example, a 5mg vial with 2 mL is 2.5 mg/mL, where 40 units equals 1 mg. The chart above covers common vial sizes.

How many units is 0.25 mg of semaglutide?

It depends on your vial's concentration. At 2.5 mg/mL, 0.25 mg is 10 units. At 5 mg/mL, it's 5 units. Divide the dose in mg by the concentration in mg/mL, then multiply by 100 to get units on a U-100 syringe.

How many units is 1 mg of semaglutide?

Divide 100 by your concentration in mg/mL. At 2.5 mg/mL, 1 mg is 40 units. At 5 mg/mL, 1 mg is 20 units. Always confirm the concentration on your vial label first.

Do Ozempic or Wegovy pens need to be mixed?

No. Ozempic and Wegovy injections are FDA-approved and supplied as ready-to-use solutions in pens or prefilled syringes. Wegovy also comes as a tablet. Only compounded semaglutide supplied as a freeze-dried powder needs reconstitution.

How long does reconstituted semaglutide last?

Follow the beyond-use date on your pharmacy label. Without one, the general rule for preserved multi-dose vials is to discard 28 days after first puncture unless the manufacturer or pharmacy says otherwise. Keep it at 2 to 8°C and never freeze it.

Is semaglutide sodium the same as semaglutide?

No. The FDA says salt forms such as semaglutide sodium and semaglutide acetate are different active ingredients from the semaglutide in approved products. The FDA also says it has no information on whether these salts behave the same way as the approved active ingredient, and knows of no lawful basis for compounding with them. Ask your pharmacy exactly what's in your vial.

What syringe should I use for semaglutide?

A U-100 insulin syringe sized to your dose. Because semaglutide doses often come out to a small number of units, a 0.3 mL (30 unit) syringe with single-unit markings is usually easiest to read accurately. Ask your pharmacy which syringe matches your prescription.

The Bottom Line

Mixing semaglutide is simple: clean surface, slow diluent, gentle swirl, clear label. The part that deserves your attention is the math, because units are a measure of volume and the same number of units can mean very different doses depending on how the vial was mixed.

Stick with a licensed prescriber and pharmacy, follow their diluent and storage instructions, and recheck your numbers any time the vial changes. If you're comparing GLP-1 options, our tirzepatide reconstitution guide and the broader weight loss peptide reconstitution guide cover the rest. The peptide calculator does the arithmetic, and PeptideKit keeps every dose and vial organized.

Always consult with qualified healthcare professionals before starting any peptide therapy protocol. This information is for educational purposes only and does not constitute medical advice.