Semaglutide Dosage Chart: Vial Size to Syringe Units

A semaglutide dosage chart maps a vial's labeled mg amount and the bacteriostatic water added to it into the number that matters at the syringe: units. Semaglutide ships as lyophilized powder, so the mg on the label is fixed, but concentration is not — it depends entirely on how much water goes into the vial. This chart works through that math for the vial sizes semaglutide research vials are commonly supplied in. It is a reference for research and educational purposes only and is not medical advice.

The reference concentration

There is no single required water volume for semaglutide. A reference point commonly cited across semaglutide research materials scales the water to the vial size at 1 mL per 5 mg, which holds the concentration at a constant 5 mg/mL no matter which vial size is on hand:

Vial size	Water added	Concentration
2 mg	0.4 mL	5 mg/mL
5 mg	1 mL	5 mg/mL
10 mg	2 mL	5 mg/mL
15 mg	3 mL	5 mg/mL

Because the ratio scales with vial size, the units for a given dose stay identical across all four rows — only the total number of doses each vial holds changes. For the full mixing procedure behind these numbers, see the semaglutide reconstitution calculator guide.

Semaglutide dosage chart by target dose

Each row below assumes the 5 mg/mL reference concentration and shows the resulting draw on a U-100 insulin syringe (100 units per mL):

Target dose	Volume	Units
0.25 mg	0.05 mL	5 units
0.5 mg	0.1 mL	10 units
1 mg	0.2 mL	20 units
1.5 mg	0.3 mL	30 units
2 mg	0.4 mL	40 units
2.5 mg	0.5 mL	50 units

A 1 mg dose landing on an exact 20-unit mark is a large part of why 5 mg/mL is the reference concentration most semaglutide charts default to — every dose in the table above reads cleanly on a standard U-100 barrel.

Reading the chart against a specific vial

Worked example. A 10 mg vial mixed with 2 mL of bacteriostatic water sits at 10 ÷ 2 = 5 mg/mL. For a 1 mg target dose: 1 ÷ 5 = 0.2 mL, and 0.2 mL × 100 = 20 units on a U-100 syringe.

Compare that to the same 1 mg dose drawn from a 5 mg vial mixed with 1 mL of water — also 5 mg/mL: 1 ÷ 5 = 0.2 mL, or 20 units again. The dose in mg is identical, and so is the unit reading, because both vials were reconstituted to the same concentration. What differs is supply: the 5 mg vial holds 5 ÷ 1 = 5 doses at 1 mg each, while the 10 mg vial holds 10 ÷ 1 = 10 doses.

Vial size sets dose count, water volume sets draw size

Vial size and water volume do different jobs, and conflating them is the most common misread of a chart like this one. Vial size sets the total mg of semaglutide available across the whole vial. Water volume sets concentration, which is what determines the units for any single draw.

At a 0.5 mg dose, a 2 mg vial provides 2 ÷ 0.5 = 4 doses. A 15 mg vial at that same 0.5 mg dose provides 15 ÷ 0.5 = 30 doses — 7.5 times the doses, because it holds 7.5 times the semaglutide (15 ÷ 2), not because it was mixed differently. Water volume, by contrast, changes only the draw size per dose, not how many doses the vial holds in total.

When your vial doesn't match the reference ratio

A vial mixed with a different water volume still follows the same formula — it just won't land on the chart above. Take a 15 mg vial mixed with 2 mL of water instead of the reference 3 mL: concentration is 15 ÷ 2 = 7.5 mg/mL. A 1 mg target dose at that concentration is 1 ÷ 7.5 = 0.1333 mL, or roughly 13.3 units — a fractional reading that doesn't sit cleanly on a syringe marked in whole units.

That's a signal to change the water volume rather than round the draw up or down. This is the case the peptide dosage calculator is built for: enter the vial size and water volume you actually used, and it runs the same concentration-to-units math for any combination, not just the round numbers in a reference chart. Its reverse mode also works the other direction — enter a target dose and a desired unit reading, and it returns the water volume that produces it.

Sourcing matters as much as the math

Every calculation in this chart assumes the vial's labeled mg amount is accurate. That assumption doesn't hold across the unregulated online market. A peer-reviewed 2024 analysis of semaglutide purchased from online sellers without a prescription measured real purity of 7.7%–14.37% against a labeled 99%, with endotoxin detected in every sample tested (JMIR, 2024). The same study found actual semaglutide content in some samples exceeded the labeled amount by roughly 29%–39% — meaning the concentration on the label didn't match what was actually in the vial (PMC, 2024).

If the actual mg content is off from the label, the concentration this chart calculates is off too, no matter how precisely the water and draw are measured. A supplier that publishes third-party Certificates of Analysis for each batch is the only way to verify that assumption before it feeds into the math above.

Common mistakes

• Reading a unit count from this semaglutide dosage chart against the wrong vial. A number in the table only applies if the vial was actually mixed to the 5 mg/mL reference concentration. Confirm the water volume used before drawing.
• Assuming vial size sets the dose. It sets the total mg available across the vial. Concentration — set by water volume — is what determines units per dose.
• Mixing up mg and mcg. Semaglutide doses are sometimes written in micrograms instead of milligrams (1 mg = 1,000 mcg). Reading 0.25 mg as 250 mcg is correct; reading it as 25 mcg or 2,500 mcg is a tenfold or tenfold-inverse error.
• Rounding mid-calculation. Carry the full decimal through the mL step and only round the final unit reading, and only if the syringe requires it.

Use the calculator

This semaglutide dosage chart covers the common 5 mg/mL reference concentration, but your vial and target dose may not match it exactly. Enter your vial size, water volume, and target dose into the free peptide calculator for an exact unit count, or run its reverse mode to find the water volume that lands a given dose on a whole unit mark. For the step-by-step mixing process, see how to reconstitute peptides, and for the full concentration walkthrough specific to this compound, see the semaglutide reconstitution calculator guide.