Handling and measurement
Gauge
Last updated
How thick a needle is, written as a number followed by G. The scale runs backwards, so a higher number is a thinner needle: 31G is finer than 29G, which is finer than 25G. Insulin syringes typically carry a 29G to 31G needle. Gauge describes thickness only.
Why it matters here
A thinner needle is more comfortable but moves liquid more slowly, which matters most when drawing from a vial rather than injecting. Thick or syrupy liquid through a very fine needle can take a surprisingly long time, and pulling hard on the plunger to hurry it is what drags air in alongside.
What it is not
Gauge is not length. Length is a separate figure given in millimetres or inches, commonly around 4 mm to 13 mm on the fine syringes, and a packet states both; reading only the gauge tells you nothing about how far the needle reaches.
Also called
- gauge
- needle gauge
- 31g
- 30g
- 29g
- 27g
- 25g
- needle thickness
- needle size
The G is simply gauge. The backwards scale comes from wire manufacturing, where the number counted how many times the wire had been drawn through a die to thin it, so more passes meant a higher number and a finer wire.
Compounds carrying this term
None on file yet. This term is in the controlled vocabulary but no compound record currently uses it — which is a statement about our coverage, not about the term.