Pen Needles (32G 4mm)

0.23 mm (32G) × 4 mm — sterile, single-use, screw-on

A screw-on pen needle for the Pioneer pen kit. Each one is 0.23 millimetres across and 4 millimetres long, sterilised with ethylene oxide, sealed individually with a paper tab, and CE marked under notified body 0197. Sold singly, in tens and in hundreds. The pen case holds three spares in its moulded recesses, so the usual pattern is to keep the case stocked and reorder in tens.

Specification at a glance#

• 0.23 mm outside diameter — 32 gauge
• 4 mm length, the shortest in common use
• Screw thread, fits the Pioneer pen kit
• Sterilised with ethylene oxide (STERILE EO)
• Individually sealed, single-use, CE 0197

Identity and specification#

What 32G × 4 mm means#

Two independent numbers, and they are easy to confuse. Gauge is the outside diameter on an inverted scale — the number climbs as the needle gets thinner, so 32G is finer than 31G, which is finer than 30G. Length is stated separately, in millimetres, and has nothing to do with gauge.

At 32G × 4 mm this is at the fine, short end of what is manufactured. The trade-off is the same one that applies to every needle: a finer lumen passes viscous solution more slowly. Material reconstituted at high concentration, or taken straight from the fridge, will resist noticeably. Letting a cartridge come up to room temperature first does more for a stiff delivery than pressing harder does.

Pen needles are not syringes#

A pen needle is a needle and a thread, nothing else. It has no barrel and no graduations, because the pen body does the measuring. That is the whole point of the system: the volume is set on the pen dial and read off a window, rather than judged by eye against marks on a barrel.

An insulin syringe is the opposite — one sealed unit, needle bonded to a graduated barrel, where the operator reads the volume directly. Neither is better. The pen is more repeatable and easier to read; the syringe is cheaper per use and does not depend on a cartridge being loaded correctly.

Why they are single-use#

The point is ground and coated for exactly one pass. After a single entry through a rubber septum the bevel is measurably deformed under magnification, which makes the next entry harder and shears small fragments from the septum. A needle left attached to a pen between uses is also an open path into the cartridge, and the contents can creep out or air can creep in — which is why a used needle comes off and goes into a sharps container rather than staying on the pen as a cap.

Handling and disposal#

• Keep them sealed, dry and at room temperature — the paper tab is the sterile barrier
• A tab that has been peeled, pierced or damp is no longer a sterile barrier; discard it
• Swab the cartridge septum with a 70% isopropyl pad and let it dry before fitting
• One needle, one use, then straight into a rigid sharps container
• Sharps containers go through a licensed disposal route in the UK, never household waste

What they fit#

These are the needles supplied with, and specified for, the Pioneer pen kit. They use the standard screw thread found on most refillable pens, but if you are fitting them to a pen bought elsewhere, check the thread on that pen rather than assuming — there is more than one standard in circulation and a needle that does not seat properly will leak.

Sizes and pricing#

Working with lyophilised peptides? See our pens, syringes and needles guide, reconstitution guide, storage guide and how to read a COA.