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Your guide to 31G pen needles and syringes

31G is the ultra-fine end of the practical needle-gauge range — what GLP-1 pens (Mounjaro, Ozempic, Wegovy) ship with, and what most people switch to when they have been on weekly injections long enough to value comfort over draw-up speed. This site collects what we have learned about 31-gauge pen needles and syringes from running an EU supplier: what 4 mm vs 5 mm vs 6 mm actually changes, how to spot a counterfeit pen needle, and the rotation pattern that keeps a year on a GLP-1 from leaving your skin like a pin cushion.

We do not sell anything here. The articles below are the notes we send first-time GLP-1 buyers when they email asking which pen needle to order. If you decide a 31G is what you want, you can pick up a sterile pack at injectkit.com — but read the technique pages first. The needle is rarely the bottleneck; the angle, the speed and the spot are.

For thicker oils where 31G will clog or bend, see our sister site 29-g.com. For the all-rounder gauge, see 30-g.com.

verified_userReviewed by clinically-trained editor linkSources cited in every article placeEU-based · independent editorial

Recent articles

Practical, source-cited writing on 31G pen needles and syringes — from the team that ships them across the EU.

GLP-1 Needle and Syringe Sizing Guide: Mounjaro, Ozempic, Wegovy and Compounded Vials

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GLP-1 Needle and Syringe Sizing Guide: Mounjaro, Ozempic, Wegovy and Compounded Vials

Mounjaro, Wegovy and Ozempic needle and syringe sizes — practical UK guidance on gauge, length and travel kit options for GLP-1 self-injection.

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4 mm vs 5 mm vs 6 mm Pen Needles for GLP-1 Injections: What the Evidence Says

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4 mm vs 5 mm vs 6 mm Pen Needles for GLP-1 Injections: What the Evidence Says

4 mm is the modern default for GLP-1 self-injection. 5 mm is fine. 6 mm and 8 mm are mostly leftover diabetes-era stock. Here's what the FITTER consensus and EMA…

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How to Inject Mounjaro: an 8-Step Protocol from the KwikPen Instructions

Mounjaro

How to Inject Mounjaro: an 8-Step Protocol from the KwikPen Instructions

Step-by-step Mounjaro KwikPen injection protocol from the Eli Lilly user manual, with the bits where first-time UK users actually get stuck.

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Mounjaro KwikPen Needles: a UK Buyer's Guide for 4 mm and 5 mm Pen Needles

Mounjaro

Mounjaro KwikPen Needles: a UK Buyer's Guide for 4 mm and 5 mm Pen Needles

What pen needles fit the Mounjaro KwikPen, what UK pharmacies actually charge, and what Lilly's instructions require. 4 mm × 31G or 32G is the modern default.

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Rotating Injection Sites for Weekly GLP-1 Medications: a 4-Week Pattern

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Rotating Injection Sites for Weekly GLP-1 Medications: a 4-Week Pattern

Lipohypertrophy is rare on weekly GLP-1 injection but not zero. Here's a simple 4-week abdomen-and-thigh rotation pattern, with the FITTER guidance behind it.

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storefront Need supplies?

When you have read enough — sterile 31G packs ship from the EU.

If you decide 31G is the right gauge for your routine, our sister shop sends sterile, individually-blistered pen needles and syringes from Spain across the EU and UK. Free shipping over €50.

Shop 31G syringes at injectkit.com arrow_forward
Imogen Whitcombe — Editor

Imogen Whitcombe

Editor · 31-g.com

Who writes here

31-g.com is the content arm of InjectKit, an EU sterile-syringe supplier operated by meeco Servicios Globales S.L. (CIF B42774703, Alicante, Spain). Articles are written by people who handle these syringes daily — and reviewed against the manufacturer's IFU before publication.

If you spot something wrong in an article, email [email protected] and a human will read it. See our editorial policy for the full version.

place EU-based verified Sterile-syringe supplier edit_note Independent editorial link Sources in every article

Frequently asked questions

Everything you want to know before ordering.

Is 31G the right gauge for me? expand_more

31 gauge is the thinnest precision needle commercially available — ideal for precision personal-use with minimal discomfort. If your prescription specifies a different gauge, follow your doctor's advice. For 29G or 30G, visit our sister sites 29-g.com or 30-g.com.

How fast will my order arrive? expand_more

Orders ship from Spain and arrive in 2-3 business days to most EU countries. Tracking number arrives by email as soon as your parcel is dispatched.

How is the package labelled? expand_more

Plain padded envelope. Sender appears as meeco SL with no product names, health terms, or brand markings on the outside. Only you will know what is inside.

What is your return policy? expand_more

Unopened, sealed packaging can be returned within 14 days of delivery for a full refund. For hygiene reasons we cannot accept returns of opened packages. Email [email protected] to start a return.

Is this a supplies? expand_more

Yes. Our syringes are high-quality medical supplies manufactured under ISO 13485. They are sterilised with ethylene oxide and individually packaged. Each batch is traceable to its manufacturing facility.

Do you ship outside the EU? expand_more

Yes. We ship to all EU member states plus Switzerland, Norway, and the United Kingdom. Delivery times outside the EU may be slightly longer (3–7 business days) and import duties may apply.