What kind of vial do you have?
Powder: you add liquid to it before the first dose.Liquid: the label shows a strength in mg/mL.
Mixing, measuring and injecting GLP-1 vials
How many units
do I draw?
We turn a prescribed dose into syringe units and cover mixing a vial, reading the syringe, and giving the shot. Each step shows the drug label it comes from.
Powder vial? Mix it first.U-100 syringe: 100 units = 1 mL
Step 1 of 425%
The formula
Units to draw = dose (mg) ÷ vial strength (mg/mL) × 100
Works on any U-100 insulin syringe, where 100 units = 1 mL.
Example
0.25 ÷ 2.5 × 100 = 10 units
0.25 mg from a 2.5 mg/mL vial (0.10 mL).
Mixing a powder vial?
5 mg ÷ 2 mL = 2.5 mg/mL
Strength = mg in the vial ÷ mL of diluent added. The strength on your vial’s label decides the answer.
Also on DosePep: printable units charts · pen guides · retatrutide watch
This is a calculator, not medical advice. It won’t tell you what dose to take. Always follow what your prescriber and pharmacist told you.
Last updated
What the label says to get right
Three things to check around the math.
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Step 1 · Only for powder vials
Mix your vial
If your vial came as a powder, add the diluent your label names, often bacteriostatic water. Some powders need a specific diluent, amount and handling that the mg alone cannot tell you. The label governs. Liquid vials are already mixed.
Get the vials ready.
Prepare the tops of both vials the way the instructions that came with your medicine say.
Press space to play or pause, or use your arrow keys.
01 / prepare
Always follow the instructions that came with your medicine. Read the full guide →
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Step 2
Pick your syringe and needle
Here’s the same 10‑unit dose in three syringe sizes. On the smaller ones the lines sit farther apart, so it’s easier to see where to stop.
Same dose, three syringes
Drawn to scale next to each other. Pick an amount to compare.
0.3 mL
30 units
0.5 mL
50 units
1.0 mL
100 units
Always go by the lines printed on your own syringe. The FDA has reported dosing errors when people mixed up mL, mg and units, or used a syringe much bigger than their dose.
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Higher G means a thinner needle.
Our needle guide lists 30G × 12.7 mm and 31G × 6 or 8 mm.
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Length matters too.
Check the gauge and length printed on the package.
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Pen needles are a different kind.
They don’t fit syringes.
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Step 3
Give your injection
A shot just under the skin of your stomach area, start to finish. Always inject the way your healthcare provider showed you.
Injection sites guideWhere the label allows.
The Zepbound instructions say to inject in the stomach (abdomen) or thigh. Another person may use the back of the upper arm. Rotate sites, and do not inject where the skin is tender, bruised, scaly or hard, or into scars or damaged skin.
Press space to play or pause, or use your arrow keys.
01 / choose
Always follow the instructions that came with your medicine. Read the full guide →
Units, mL and mg are not the same thing
The little numbers on an insulin syringe are units, not milligrams. How much medicine is in each unit depends on your vial, so the answer changes whenever the vial does.
Read: units vs mL vs mgAlmost all of the math comes down to one fact about U‑100 syringes, the kind this calculator is built for.
100 units
in every 1 mL
5×–20×
the intended dose. That’s what some people took in the compounded semaglutide cases the FDA warned about in July 2024, after mixing up mL, mg and units.
0.01 mL
is one unit on a U‑100 syringe. So 10 units is 0.1 mL.
Show the result to your pharmacist before you rely on it. A second pair of eyes is always worth it.
0.25 mg is not 25 units
If your vial has 2.5 mg in each mL, 0.25 mg is 10 units. A vial with a different strength gives a different number.
30 units
The smallest of the three common syringe sizes (0.3 mL). Its lines sit farther apart, so small doses are easier to read.
Compare syringe sizesPick your medicine
Each page has a calculator already set up for that medicine, with the label doses ready to choose, plus a table of the usual dose steps.
Semaglutide
Facts about named FDA-approved injectable products. Ozempic’s labeled maximum is 2 mg once weekly. Wegovy’s 7.2 mg dose comes only as the pre-filled Wegovy HD pen, not from a vial.
- Sold as
- Ozempic, Wegovy
- Label doses
- 0.25 mg to 2.4 mg
Tirzepatide
Facts about named FDA-approved injectable products. These label schedules are not a recommendation for any other product.
- Sold as
- Mounjaro, Zepbound
- Label doses
- 2.5 mg to 15 mg
More dose references: printable semaglutide units chart, printable tirzepatide units chart, and convert units back to mg.
Retatrutide
Not FDA‑approvedStill being studied, so there’s no label dose. The calculator shows doses used in clinical trials (2 mg to 12 mg), for reference only.
Read about the trial dosesUsing a pen instead?
Pens don’t use syringe units, so the unit math here doesn’t apply. Pick your pen to see what its label says about using it.
These schedules and vial strengths apply only to the named products. They say nothing about any other product.
Learn the basics
Short guides in plain language. Each one links to the label or study it came from.
All guidesQuick answers
How many units is 0.25 mg of semaglutide?
It depends on your vial's strength. At 2.5 mg/mL, 0.25 mg is 10 units. At 5 mg/mL, 0.25 mg is 5 units on a U-100 syringe.
How do I convert units back to mg?
mg = units ÷ 100 × strength (mg/mL). For example, 10 units at 2.5 mg/mL = 0.25 mg.
How much bacteriostatic water should I add?
Follow the amount on your pharmacy's label or instructions. We don't choose it. For example, 5 mg + 1 mL gives 5 mg/mL, while 5 mg + 2 mL gives 2.5 mg/mL.
Is 1 unit the same as 1 mg?
No. A unit is a volume mark. On a U-100 syringe, 1 unit = 0.01 mL. How many mg are in it depends on the strength.
Which syringe size should I use?
The calculator shows U-100 syringes in these sizes: 0.3 mL is 30 units, 0.5 mL is 50 units, 1 mL is 100 units. Smaller syringes have more space between lines, so small amounts are easier to read. Use the syringe your pharmacy gave you.
Why is my number different from what my pharmacy said?
Usually, the strength is different. The label on your vial and your pharmacist are right. Ask them to check the strength and the syringe with you.
Can I use this for Ozempic or Mounjaro pens?
No. Pens don't use syringe units.
Double-check the math every time
It takes about 20 seconds. Have your prescription and your vial in front of you while you check it.
Back to the calculatorMedically reviewed by Ashley Alexis, NDLast reviewed How we review