What are the different pen needle sizes?

Pen needles range in length from 4 mm to 12.7 mm and in gauge from 29G to 33G. The longest size has two published figures: Owen Mumford and Ypsomed call it 12 mm, embecta and UltiMed call it 12.7 mm, which is one half inch.

Pen needle gauge and tube outer diameter

Pen needle gauge sizes range from 29G to 33G, with outer diameters from 0.203 mm to 0.320 mm per FDA filing K210864. The thinnest 33G outer diameter of 0.203–0.216 mm matches ISO 9626 Table 1, and 29G is the gauge on every 12 mm and 12.7 mm needle in the table above. What a gauge number means is set out in needle gauges explained, and the per-gauge dimensions in the needle gauge chart.

4mm pen needles and ultra-thin wall technology

In AccessGUDID, embecta's registered descriptions include 'UTW' (Ultra Thin Wall), such as model 320550. embecta's product page claims its ultra-thin wall is the highest ISO standard for a 32G pen needle inner diameter, citing ISO 9626. Novo Nordisk and Ypsomed AG anchor compliance claims to the ISO 11608-2 pen needle standard. Novo Nordisk filing K133738 cites ISO 11608-2:2012 for the NovoFine Plus 32G × 4 mm. It lists its own as '32G Tip' and the BD predicate as '32G'. Ypsomed filings cite standard titles in full. K110312, prepared in 2011, cites 'Pen-injectors for medical use - Part 2: Needles - Requirements and test methods'. K122971, filed in 2012, cites 'Needle based injection systems for medical use - Requirements and test methods - Part 2: Needles'.

Comparing insulin pen needle sizes across manufacturers

At the long end the two figures are 12 mm and 12.7 mm. Owen Mumford and Ypsomed publish 12 mm; embecta and UltiMed publish 12.7 mm, which is one half inch exactly. Every one of those products is 29G. No source retrieved explains the split.

The same imperial residue is visible inside a single FDA filing. Sandstone's K210864 prints metric and imperial labels side by side, and they do not convert into each other: 3/16 inch is labelled 5 mm, 1/4 inch is labelled 6 mm, 5/16 inch is labelled 8 mm. Only 5/32 inch, which is 3.97 mm, rounds cleanly to its 4 mm label.

Gauge does not follow from length. Owen Mumford publishes 5 mm at both 30G and 31G; UltiMed publishes 6 mm at both 31G and 32G; Sandstone's filing lists 5 mm at 30G, 31G and 32G. A length alone does not identify a needle, and neither does a gauge.

An NHS regional formulary listing, whose document footer is dated January 2024 while the file it is posted as carries a 2026 date, has the widest cross-manufacturer grid retrieved here, and it makes the same point across many more lines. In that listing 4 mm appears at 31G, 32G and 33G; 5 mm at 30G, 31G and 32G; 6 mm at 31G and 32G; 8 mm at 30G, 31G and 32G; 10 mm at 29G and 30G; and 12 mm at 29G. Not one line in it publishes 12.7 mm. Every line that goes past 8 mm stops at 10 mm or 12 mm.

The syringe side of the same drawer is covered separately: how to read an insulin syringe and insulin syringe sizes. One published figure exists for how many pen needles a container holds — 300 in a 1.4-quart container, on sharps container sizes.

Sources

• Food and Drug Administration (FDA) 510(k) Summary K210864
• Food and Drug Administration (FDA) 510(k) Summary K133738
• Food and Drug Administration (FDA) 510(k) Summary K122971
• Food and Drug Administration (FDA) 510(k) Summary K110312
• ISO 9626:2016 Specification Preview
• FDA AccessGUDID Device Record
• embecta BD Ultra-Fine Storefront
• embecta BD Nano 2nd Gen Product Page
• Owen Mumford US Unifine Pentips Page
• UltiMed UltiCare Pen Needles Page
• UltiMed UltiCare VetRx Animal Health Page
• Novo Nordisk Needle Portfolio Page
• NHS Regional Knowledge Service Formulary Listing

Specifications last verified: 2026-08-06