Basics & Technique
How do I read an insulin syringe?
Updated 2026-05-02
Your syringe has tiny tick marks. Each small mark is one unit. 100 units fills up exactly 1 mL. The number you fill the syringe to is your units. Read the bottom of the curved liquid line, not the top. Almost every peptide uses a U-100 syringe. If you pick up a U-40 syringe by mistake, your dose will be way off.
IfIf your vial says 5 mg/mL and your dose is 1 mg
Thenthen draw to the 20-unit mark on a U-100 syringe
IfIf you see air bubbles
Thenthen tap the syringe so they rise, push them back into the vial, and redraw
IfIf the syringe says U-40
Thenthen stop and get a U-100 before injecting
Key facts
- U-100 syringe: 100 units = 1 mL; 1 unit = 0.01 mL
- U-40 syringe: 40 units = 1 mL; 1 unit = 0.025 mL (mostly veterinary)
- Common sizes: 0.3 mL (30u), 0.5 mL (50u), 1.0 mL (100u)
- U-100 is the standard for compounded GLP-1 vials
- Quick math: dose in mg, divided by the vial's mg/mL, times 100, equals units on a U-100 syringe
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