Quick reference

Syringe key

A friendly visual guide to syringe sizes and how to read their measurements.

Know your graduations

Every syringe is divided a little differently. The lowest dose you can measure depends on how many lines fit between the big numbers: divide the capacity by the number of divisions and you have your smallest reliable measurement.

Tuberculin (1 mL)

smallest mark: 0.01 mL

Intradermal tests (PPD/allergy) and very small subcutaneous doses.

milliliters (mL)

Standard (3 mL)

smallest mark: 0.1 mL

The everyday workhorse: most subcutaneous and IM injections.

milliliters (mL)

Medium (5 mL)

smallest mark: 0.2 mL

Larger IM doses that won't fit comfortably in a 3 mL.

milliliters (mL)

Large (10 mL)

smallest mark: 0.2 mL

Drawing up, reconstituting, and flushing lines.

milliliters (mL)

Insulin (U-100, 1 mL)

smallest mark: 1–2 units

Insulin ONLY. Calibrated in units, never in mL.

units

Find the big marks first

Locate the labeled milliliter (or unit) lines, then count the small lines between them to know the value of each division.

Read at the ring

Line your dose up with the front (top) edge of the rubber plunger tip, not the raised dome or the very bottom.

Match the syringe to the volume

Pick the smallest syringe that fits the dose. A snug fit means more graduation lines and a more accurate measurement.

TB is not insulin

Tuberculin and insulin syringes look alike but are calibrated completely differently. Insulin is measured in units. Never draw up other medications in it.

Safety: always double-check the concentration and the ordered dose, use aseptic technique, and dispose of every needle in an approved sharps container immediately after use. This page is an educational reference, not a substitute for institutional policy or clinical training.