Semaglutide Dosage Calculator

Concerned about side effects? See Semaglutide side effects — what the research documents (honest, sourced, research-use-only).

The semaglutide dosage calculator on this page exists to answer one deceptively simple question: once you have reconstituted a lyophilized vial with bacteriostatic water, how many units do you pull into a U-100 insulin syringe to land on a given milligram dose? Semaglutide is supplied as a dry powder measured in milligrams, but your syringe is marked in insulin units and milliliters. The gap between those two scales is where almost every mistake happens. This page walks through the exact math, gives you a fully worked example with real catalog numbers, and lays out titration and vial-size tables so you can check any figure by hand. Everything here is reference information you can verify line by line against your own vial, syringe, and target dose.

Semaglutide is a GLP-1 receptor agonist that has been studied for weight loss and glycemic control. In the STEP program, participants saw roughly a 15% mean reduction in body weight over 68 weeks, and it is administered once weekly by subcutaneous injection. Because the compound is so potent per milligram, small errors in reconstitution translate into large errors at the needle — which is exactly why running the numbers, rather than eyeballing them, matters.

How the semaglutide dosage calculator works

Every reconstitution reduces to four numbers, and the semaglutide dosage calculator computes all four from just three inputs you supply: the vial strength in milligrams, the volume of bacteriostatic water you add in milliliters, and your target dose in milligrams. The relationships never change:

The only conversion you need to keep straight is that 1 mL equals 100 units on a U-100 insulin syringe, and that 250 mcg is the same as 0.25 mg. Milligrams are the currency of the dose; units are the currency of the syringe. Concentration is the exchange rate between them, and it is set entirely by how much water you add. Add less water and the same milligram dose occupies fewer units; add more water and it occupies more. Nothing about the powder itself changes — only how the dose is spread across the liquid.

Why the amount of water is a choice, not a rule

A common point of confusion is that people expect a “correct” volume of bacteriostatic water printed somewhere. There isn’t one. The water volume is yours to pick, and it only affects how the dose reads on the syringe, never the milligram amount delivered. A practical goal is to choose a volume that makes your typical dose land on an easy-to-read number of units — ideally not so few units that a tiny slip is a big percentage error, and not so many that it exceeds the syringe barrel. For most semaglutide vials on this site, 1 mL to 2 mL of bacteriostatic water produces clean, readable numbers. The peptide reconstitution guide covers the mechanics of adding water gently down the vial wall and swirling rather than shaking.

If you would rather work backward — deciding first what unit reading you want, then how much water to add — the same formula rearranges cleanly: water (mL) = units × vial mg ÷ (dose mg × 100). Say you want a 0.25 mg dose to read as an easy 10 units on a 10 mg vial: 10 × 10 ÷ (0.25 × 100) = 4 mL. Reconstituting that vial in 4 mL instead of 2 mL doubles the volume per dose and moves the same 0.25 mg from 5 units to 10 units, without changing a single milligram delivered. That is the whole trick: the water volume is a dial for readability, and you can turn it in either direction before you ever touch the syringe.

Worked example: 10 mg vial, 2 mL water, 0.25 mg dose

Let’s run the calculator by hand using a real configuration available on this site: a 10 mg vial reconstituted with 2 mL of bacteriostatic water, targeting a first-step dose of 0.25 mg, drawn on a U-100 syringe.

1. Concentration = 10 mg ÷ 2 mL = 5 mg/mL. Every milliliter of your reconstituted solution now carries 5 mg of semaglutide.
2. Draw volume = 0.25 mg ÷ 5 mg/mL = 0.05 mL. That is the physical amount of liquid your 0.25 mg dose occupies.
3. Units = 0.05 mL × 100 = 5 units. On a U-100 insulin syringe, you fill to the 5-unit mark.
4. Doses per vial = 10 mg ÷ 0.25 mg = 40 doses. At a once-weekly 0.25 mg step, a single vial covers a long stretch of a starter protocol.

Notice how forgiving the arithmetic is once you have the concentration. Because 5 mg/mL means “5 units per 0.05 mg,” you can read the whole titration ladder straight off that one ratio without recomputing from scratch each time.

Semaglutide units per dose across a titration schedule

Research protocols commonly titrate semaglutide upward over several weeks rather than starting at a full dose. A widely reported schedule steps through 0.25 mg, 0.5 mg, 1.0 mg, 1.7 mg, and up to 2.4 mg once weekly, giving the body time to adjust at each rung. Using the same 10 mg vial reconstituted in 2 mL (5 mg/mL concentration), here is what each step lands at on a U-100 syringe. This is the semaglutide units per dose table most people actually want.

Every value in that table comes from dividing the dose by 5 mg/mL and multiplying by 100 — the same two operations, five times. At this reconstitution the full 2.4 mg step still fits comfortably at 48 units, well under the 100-unit barrel of a standard 1 mL insulin syringe. If you had used a different water volume, the milligram doses would be identical but the unit readings would shift, which is the entire point of running the calculator against your own vial rather than copying someone else’s units.

Semaglutide vial sizes and how they change the units

This site references three semaglutide vial strengths: 5 mg, 10 mg, and 20 mg. Holding the water volume constant at 2 mL and the dose at the 0.25 mg first step, here is how vial size alone moves the concentration and the units per dose. The dose in milligrams stays exactly the same across all three rows — only the syringe reading and the number of doses per vial change.

The 20 mg vial concentrates the powder so much that a 0.25 mg dose is only 2.5 units — a reading that sits between marks on many syringes and is easy to misjudge. That is a case where adding more water, not less, gives you a more readable dose. The 5 mg vial does the opposite, spreading the first step across a comfortable 10 units. There is no single “best” vial; the right one depends on which doses you plan to draw most often and how precisely your syringe is marked. For documented specifics on any given compound, the single-peptide dosage reference lists the source figures.

How to read the units on a U-100 syringe

A U-100 insulin syringe is calibrated so that 100 units equals 1 mL. The barrel is usually printed in even numbers — 5, 10, 15, 20, and so on — with a minor tick every 1 or 2 units depending on the syringe. To fill to 5 units, you draw until the plunger’s leading edge reaches the 5 mark. Because semaglutide doses at the low end occupy very few units, a smaller-capacity syringe (0.3 mL / 30 units) often has finer, more widely spaced markings and makes small draws like 5 or 10 units much easier to read accurately than a full 1 mL barrel does. Always read at eye level and confirm the plunger edge, not the needle tip, sits on your target mark.

Mistakes the calculator is built to catch

• Confusing mg with mcg. 0.25 mg is 250 mcg. Entering “250” as milligrams instead of “0.25” inflates the dose a thousandfold. The calculator keeps you in one unit — milligrams — for the dose field.
• Assuming a fixed water volume. There is no mandated amount of bacteriostatic water. Copying someone else’s “units” without matching their exact vial size and water volume produces the wrong dose.
• Reading mL as units. A 0.05 mL draw is 5 units, not 0.05 units. The ×100 step is where people drop or add a decimal.
• Over-concentrating high-strength vials. As the 20 mg row shows, a strong vial in little water can push a low dose down to 2–3 units, below the resolution most people can measure reliably.
• Forgetting to round doses-per-vial down. You can only draw whole doses; a vial that computes to 40.0 doses gives 40, and any fractional result is floored.

What semaglutide is studied for — framed honestly

Semaglutide has been researched primarily for weight management and blood-glucose regulation as a long-acting GLP-1 receptor agonist. The often-cited ~15% mean body-weight reduction comes from the STEP clinical trial program and reflects trial averages over roughly a year, not a promise for any individual. It is given once weekly because of its long half-life. None of the numbers on this page are a recommendation to dose yourself; they are the arithmetic of reconstitution, provided so that anyone reading a protocol can verify the figures independently. Research use only — this is not medical advice, and it does not replace guidance from a qualified professional.

Putting it together

The whole workflow is: pick your vial, decide on a water volume that makes your common doses land on readable units, then let the four formulas do the rest. Concentration is set the moment you add water; every dose after that is just dose ÷ concentration × 100. Run your own numbers in the semaglutide dosage calculator above, cross-check them against the titration and vial-size tables here, and if anything still doesn’t line up, ask the OpenPeptide assistant to walk through your specific vial, water volume, and target dose step by step. For the documented source figures behind any compound, keep the single-peptide dosage reference open alongside.