What does 31G mean on a syringe?
Needle thickness, counted backwards: a bigger number is a thinner needle. 31G is hair-thin; 18G is thick and generally used for drawing liquid, not injecting. Sizes decoded →
Why it matters when you shop
Gauge is the first number on every syringe and needle listing, and it runs backwards: a bigger number is a thinner needle. Listings that say only "fine" or "ultra-thin" without a gauge are hiding it.
What to look for on the listing
- The gauge printed as a number with a G: 29G, 30G, 31G, 32G.
- Whether it comes on a fixed-needle syringe (insulin type) or as a separate needle for a luer syringe.
- The length beside it ("31G 5/16" or "31G 8 mm"); gauge is thickness, not length.
Go deeper
- Guide: Needle gauge chart: 18G to 32G, and what each is for
- Comparison: 31G vs 30G Insulin Syringes
- Tool: Product Finder for this category
- All terms: the glossary
Products with this specification
Insulin Syringes 31G, 0.5 mL Gauge: 31GInsulin Syringes 31G, 0.3 mL Gauge: 31GInsulin Syringes 30G, 1 mL Gauge: 30GHalf-Unit Insulin Syringes, 0.3 mL Gauge: 31GBlunt Fill Needles, 18G Gauge: 18GLuer Needle Tips, 27G Gauge: 27GPen Needles 32G Gauge: 32G
Last edited . Equipment only: nothing on this page is advice about what to inject, how much, or whether a product is fit to use. That comes from the product's labelling and whoever supplied it. Product pages link to your own country's Amazon store through affiliate links; your price is the same.