31G or 32G: does it matter
We stock 31G × 6mm. Gauge is thickness, and a higher number means thinner. Length is length, and 6mm reaches the fat layer under the skin on most people, with a light pinch if you are lean.
Two numbers, and only one of them matters much
A pen needle is described as gauge by length, so 31G × 6mm is 31 gauge and six millimetres long. Gauge runs backwards: a higher number is a thinner needle. Length is exactly what it sounds like.
| Size | Diameter | Feel | Best for |
|---|---|---|---|
| 31G × 6mm | 0.25mm | Fine, and stiff enough to place easily | What we stock. Most people, most sites |
| 32G × 4mm | 0.23mm | Slightly finer, flexes a little more | Sold elsewhere, for anyone who wants the shortest option |
Why gauge barely matters at these sizes
The difference between 31G and 32G is two hundredths of a millimetre. In blind comparisons most people cannot tell them apart. What they can tell apart is a fresh needle from a reused one, and a cold liquid from one that has come up to room temperature. Chase those instead.
The one practical difference is stiffness. A thinner needle flexes slightly more, which some people notice when placing it. That is one reason we stock 31G: it feels definite when placing it.
Why length matters more
A 6mm needle goes into the subcutaneous layer on the abdomen, thigh and upper arm, usually without a pinched fold. Skipping the pinch also avoids a common beginner error, which is squeezing so hard the tissue is compressed.
Longer needles are a hangover from thicker steel and different sites. Modern commercial pens use needles of 4mm to 6mm for exactly this reason. If you are very lean, use 6mm with a light pinch.
Never reuse a pen needle. The tip blunts on the first pass and the silicone coating strips off, so the second injection hurts more. A new one costs about ten pence.
Questions
- Will these fit my pen?
- If it takes standard screw-on pen needles, yes. That thread is universal across every pen we sell and every commercial pen we know of.
- Do you sell shorter needles?
- No, we stock 31G × 6mm only. If you are very lean, a light pinch keeps a 6mm needle in the fat layer.
- How many needles will I get through?
- One per injection. A box of a hundred is about three months daily, or most of a year twice weekly.
Pen Needles 31G × 6mm, 10 pack
Ten 31G × 6mm pen needles.