Compounded GLP-1s come in multi-dose vials with concentrations you need to calculate yourself. Here's the plain-math guide so you always draw the right dose — no errors, no confusion.
⚠️ Important Safety Note: These calculations are educational guides only. Always confirm your specific dose volume with your prescribing provider before drawing your first injection from any new vial. Concentrations vary by pharmacy and formulation — never assume your new vial is the same concentration as the last one without checking the label.
When you get brand-name Wegovy or Zepbound, the dose is pre-measured in a single-use auto-injector pen. You just click and inject the preset amount. Simple.
Compounded semaglutide and tirzepatide are typically supplied in multi-dose vials — small glass bottles with a rubber stopper that you draw from using a syringe. The vial contains a specific concentration of medication in a liquid solution, and you need to draw the correct volume to get your prescribed dose.
Getting this wrong can mean under-dosing (less effect, slower progress) or over-dosing (amplified side effects, potentially dangerous with some formulations). It's not complicated math, but it requires understanding the relationship between dose, concentration, and volume.
Everything starts with one simple equation:
Example: You need 0.5mg of semaglutide. Your vial is 2.5mg/mL concentration.
0.5mg ÷ 2.5mg/mL = 0.2mL
That's it. Every calculation you'll ever do comes back to this formula. The only variable is the concentration of your specific vial — which is printed on the label and in the paperwork from your compounding pharmacy.
Compounding pharmacies use a variety of concentrations. The most common for semaglutide as of 2026 are 2.5mg/mL and 5mg/mL, though you may encounter others. Here are worked examples for the standard titration schedule at each common concentration:
| Prescribed Dose | @ 2.5mg/mL | @ 5mg/mL | @ 10mg/mL |
|---|---|---|---|
| 0.25mg | 0.10 mL | 0.05 mL | 0.025 mL |
| 0.5mg | 0.20 mL | 0.10 mL | 0.05 mL |
| 1.0mg | 0.40 mL | 0.20 mL | 0.10 mL |
| 1.7mg | 0.68 mL | 0.34 mL | 0.17 mL |
| 2.4mg | 0.96 mL | 0.48 mL | 0.24 mL |
Tirzepatide is typically supplied at higher concentrations because the therapeutic doses are larger (in mg terms). Common concentrations are 5mg/mL, 10mg/mL, and 50mg/mL (the latter particularly in higher-dose vials). Always check your specific vial label.
| Prescribed Dose | @ 5mg/mL | @ 10mg/mL | @ 50mg/mL |
|---|---|---|---|
| 2.5mg | 0.50 mL | 0.25 mL | 0.05 mL |
| 5mg | 1.00 mL | 0.50 mL | 0.10 mL |
| 7.5mg | 1.50 mL | 0.75 mL | 0.15 mL |
| 10mg | 2.00 mL | 1.00 mL | 0.20 mL |
| 15mg | 3.00 mL | 1.50 mL | 0.30 mL |
Some providers send pre-dosed syringes or auto-injectors that eliminate the calculation entirely.
Insulin syringes are the standard tool for drawing from GLP-1 vials. They're available in 0.5mL and 1mL sizes, marked in units (U). For GLP-1 calculations, you'll typically be working in milliliters (mL), so it helps to know that on an insulin syringe: 1mL = 100 units on the syringe scale.
Example: You need 0.20mL → draw to the 20-unit mark on the insulin syringe.
You need 0.48mL → draw to the 48-unit mark.
Always draw slowly and check the meniscus (the bottom of the liquid curve in the syringe barrel) against the measurement markings. Tap the syringe gently and push out any air bubbles before injecting.
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