How-to guide
How to read your GLP-1 prescription
Compounded GLP-1 prescriptions and labels are written in several formats. Whatever the format, you are looking for the same two numbers: the vial concentration and your prescribed dose.
The two numbers you need
- Vial concentration: how much medication is in each mL, for example 5 mg/mL.
- Prescribed dose: how many mg to take each time, for example 0.5 mg.
The dose and the concentration can look alike. Typing the concentration as the dose, or the reverse, can give several times the intended amount. DoseCompa pauses and asks you to check when a dose looks like a concentration, but read the label carefully either way.
Common formats
Concentration written as mg/mL
Made-up exampleSemaglutide 5 mg/mL. Inject 0.1 mL (0.5 mg) once weekly.
- Concentration: 5 mg/mL, written directly.
- Prescribed dose: 0.5 mg.
- "0.1 mL" is the volume, not the dose.
Calculated: (0.5 ÷ 5) × 100 = 10 units (0.1 mL).
Total amount and volume
Made-up exampleSemaglutide 5 mg/2 mL. Inject 0.5 mg once weekly.
- Concentration: 5 mg ÷ 2 mL = 2.5 mg/mL.
- Prescribed dose: 0.5 mg.
Calculated: (0.5 ÷ 2.5) × 100 = 20 units (0.2 mL).
Concentration per 0.5 mL
Made-up exampleTirzepatide 5 mg/0.5 mL. Inject 2.5 mg once weekly.
- Concentration: 5 mg per 0.5 mL = 10 mg/mL. In DoseCompa, choose "mg per 0.5 mL" and enter 5.
- Prescribed dose: 2.5 mg.
Calculated: (2.5 ÷ 10) × 100 = 25 units (0.25 mL). On a syringe marked every 2 units, 25 falls between the 24 and 26 lines.
Volume only
Made-up exampleTirzepatide 10 mg/mL. Inject 0.25 mL once weekly.
- Concentration: 10 mg/mL.
- No mg dose is written. 0.25 mL × 10 mg/mL = 2.5 mg. Confirm that dose with your prescriber.
Calculated: 0.25 mL is 25 units on a U-100 syringe.
Added ingredients
Some compounded vials list another ingredient, such as "Semaglutide/B12". The GLP-1 concentration on the label is the number to use. If the label does not make clear which number belongs to the GLP-1 medication, ask the pharmacy.
Before you draw
- Find the concentration, from the vial label if the prescription is unclear.
- Find your prescribed dose in mg.
- Calculate, and compare with any unit count on your prescription.
- If they do not match, call your pharmacy before you draw.
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
My prescription and my vial label show different concentrations. Which do I use?
The vial in your hand is what you are measuring from, so its label matters. A difference can mean the pharmacy changed formulation, so call the pharmacy to confirm before you draw.
My new vial has a different concentration than my last one. Did my dose change?
Not necessarily. A new concentration changes the unit count for the same mg dose. Whether your mg dose changed is set by your prescriber, so check your prescription or ask.
My format is not shown here. What do I do?
You still need two things: the concentration in mg/mL and your dose in mg. If you cannot find both, ask the pharmacy: what is the concentration of my vial in mg/mL, and what is my dose in mg?
My prescription only says a number of units. Is that enough?
A unit count only fits the vial concentration and syringe it was written for. Ask your prescriber or pharmacist to confirm your dose in mg and the concentration of your vial.