Insulin Syringe Sizes Explained: U-100, Barrel Volume and Needle Gauge

Insulin syringes are the workhorse of subcutaneous protocols, but the labelling confuses newcomers. Here's what the numbers mean and how to pick the right one.

What “U-100” means

U-100 refers to the concentration scale the syringe is graduated for: 100 units per millilitre. It's the global standard. The unit markings let you measure small doses precisely — handy well beyond insulin itself.

Barrel volume: 0.3, 0.5 or 1 mL

The barrel sets your maximum dose and how fine the graduations are. A 0.3 mL barrel gives the tightest, easiest-to-read markings for very small doses; 0.5 mL is a middle ground; 1 mL handles larger volumes. Choose the smallest barrel that comfortably holds your typical dose — smaller barrels are easier to read accurately.

Fixed needle gauge

Most insulin syringes have a permanently attached fine needle, commonly 29G, 30G or 31G at short lengths (5/16" to 1/2"). Higher gauge = thinner = more comfortable for subcutaneous delivery. See the full needle gauge guide for the breakdown.

Why fixed-needle matters

A fixed needle has almost no dead space — the gap where product is wasted after injecting. For expensive solutions that adds up. Fixed-needle syringes also mean fewer parts to handle.

Colour coding for busy rooms

Colour-coded options like Unisharp syringes let you assign a colour per client, protocol, or day — a simple way to cut treatment-room mix-ups.

General information for professional purchasers, not medical advice. Products supplied for legitimate professional, clinical, and personal medical use only.