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 you need to turn the dose you and your provider decided on into syringe units

Thenthen use the reconstitution calculator to convert it so you draw to the right mark

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
The reconstitution calculator turns the dose you and your provider decide on into the number of units to draw, so you do not have to do the math by hand

Sources

GOVERNMENT HEALTH

MedlinePlus - how to give an insulin injection

MEDICAL INSTITUTION

Johns Hopkins Arthritis Center - subcutaneous injection technique

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