Guide
What does mg/mL mean on a GLP-1 vial?
The mg/mL number on a compounded semaglutide or tirzepatide vial tells you how concentrated it is. Together with your prescribed dose, it decides how many units you draw.
What mg/mL means
mg/mL means milligrams per milliliter: how much medication is in each milliliter of liquid in the vial.
- A 5 mg/mL vial has 5 mg of medication in every 1 mL.
- A 10 mg/mL vial has 10 mg in every 1 mL, so it is twice as concentrated.
- A 2.5 mg/mL vial is more dilute, so the same mg dose takes more liquid.
The concentration does not change your prescribed dose in mg. It changes how much liquid, and so how many syringe units, that dose takes.
If you use the wrong concentration, the number of units will be wrong. For example, using 5 mg/mL math with a 10 mg/mL vial gives twice the intended dose. Check the concentration on the vial in your hand, especially when a refill or a new pharmacy changes it.
From mg to syringe units
Compounded GLP-1 vials are usually measured with U-100 insulin syringes, where 100 units equals 1 mL. The math is the same on any U-100 syringe:
Syringes differ in how much they hold (30, 50 or 100 units) and in how often a line is printed (often every 1 unit on 30 and 50 unit syringes, every 2 units on 100 unit syringes). Check the numbers printed on yours.
Worked examples
| Medication | Dose | Concentration | Calculated units | Volume |
|---|---|---|---|---|
| Semaglutide | 0.25 mg | 5 mg/mL | 5 | 0.05 mL |
| Semaglutide | 1 mg | 5 mg/mL | 20 | 0.2 mL |
| Semaglutide | 1 mg | 10 mg/mL | 10 | 0.1 mL |
| Semaglutide | 1 mg | 2.5 mg/mL | 40 | 0.4 mL |
| Tirzepatide | 2.5 mg | 10 mg/mL | 25 | 0.25 mL |
| Tirzepatide | 5 mg | 10 mg/mL | 50 | 0.5 mL |
| Tirzepatide | 5 mg | 16.6 mg/mL | about 30.1 | about 0.301 mL |
Examples only. Use your own prescribed dose and your own vial label. Some results, like 30.1 units, fall between printed lines on every syringe, and 25 units falls between the lines of a syringe marked every 2 units. When that happens, ask your pharmacist or prescriber how to measure the dose.
The same 1 mg dose is 20 units from a 5 mg/mL vial and 10 units from a 10 mg/mL vial. The mg dose is the same; the volume is different.
Why concentrations vary
There is no single standard concentration for compounded GLP-1 medications. Each pharmacy chooses its own formulation and vial sizes, so two vials of the same medication can have different mg/mL values. Some labels also add other ingredients, such as B12. The concentration on the label is what the calculation uses.
How to read the label
- Medication name: matches what you were prescribed.
- Concentration: usually written as mg/mL. Some labels write it per 0.5 mL instead (for example "5 mg per 0.5 mL", which is 10 mg/mL). DoseCompa lets you enter either format.
- Total amount and volume: for example "10 mg/2 mL". Divide to get mg/mL: 10 ÷ 2 = 5 mg/mL.
- Beyond-use date: do not use the vial after this date.
If you cannot tell which number is the concentration, call the pharmacy before you draw.
New vial? Recalculate
Whenever you get a new vial, whether it is a refill, a new pharmacy or a different product, recalculate from the concentration on the new label. Do not assume it matches your last vial. See Switching pharmacies.
Check your numbers. Enter your vial concentration, your prescribed dose and your syringe, and DoseCompa shows the calculated units and where they fall on your syringe's printed lines.
Open the calculatorQuestions
What does mg/mL mean on a semaglutide or tirzepatide vial?
It is milligrams per milliliter: the amount of medication in each mL of liquid. A 5 mg/mL vial has 5 mg in each mL.
How do I turn mg/mL into syringe units?
Calculated units = (dose in mg ÷ concentration in mg/mL) × 100, on a U-100 insulin syringe. For example, 1 mg at 5 mg/mL is 20 units. Then check where that amount falls on your syringe's printed lines.
Is a higher mg/mL stronger?
A higher mg/mL means more medication in each mL, so the same mg dose takes less liquid. Your dose is the number of mg your prescriber set, not the concentration of the vial.
My new vial has a different concentration. What do I do?
Recalculate with the new concentration before you draw, and do not reuse the unit count from your old vial. If anything about the label or the result is unclear, ask your pharmacist.