Mounjaro Needles: What You Need and What to Do With Them

In the UK, Mounjaro comes as the KwikPen, and it needs a separate pen needle for every injection. The needles are not in the Mounjaro box, which catches people out. Here's what fits, how to use them and how to get rid of them safely.

The KwikPen and its needles

The KwikPen is a multi-dose pen holding four weekly doses in one device, with a dial you set before each injection. It needs a separate pen needle screwed on before each dose. The needles are not included in the Mounjaro pack; every Solira order includes the pen needles you need.

Which needles fit the KwikPen

Standard pen needles fit, the same type used across most injection pens. Two things matter:

• Length: 4 mm is the standard choice. Long enough to reach the fatty layer under the skin in adults of any size, short enough to reduce the risk of going into muscle, which stings more and can alter how the medicine is absorbed. 5 mm is also fine if that's what you've been given.
• Gauge: 31G or 32G. The higher the number, the thinner the needle. Thinner needles hurt less.

You don't need anything specialist or branded. A 4 mm, 32G pen needle is the sensible default for most people.

The rules that actually matter

Use a new needle every single time. This is the one people cut corners on and it's worth being firm about. A used needle is blunted after one injection, the tip bends microscopically, which makes the next injection hurt more. It also risks blocking, which can mean you don't get your full dose without realising it. And it raises the chance of infection at the site.

Take the needle off after injecting. Leaving it attached lets air into the cartridge and can let medicine leak out, both of which affect the next dose.

Hold the dose knob in for a slow count of 5. Push it in until it stops and keep holding it while you count slowly to 5. Check the dose window shows 0 before you take the needle out. See our injection guide for the full technique.

Where to inject

The abdomen (at least 5cm from the navel) or the front of the thigh. The back of the upper arm can also be used, but someone else should give that injection for you. Rotate the site each week rather than using the same spot, repeatedly injecting one area can cause the tissue underneath to thicken, which affects absorption.

Sharps disposal: do not put them in the bin

Used needles and pens are clinical sharps waste. They must not go in your household rubbish or recycling, where they're a genuine injury risk to waste workers. What to do instead:

1. Get a sharps bin. You can add a 1 litre sharps bin to your Solira order for £2.99, or ask your GP practice or local council.
2. Put the used needle in straight after injecting. Carefully put the outer needle cover back on (never the small inner cover), unscrew the needle and drop it into your sharps bin. Keep the pen, with its cap on, for your next dose: each pen holds 4 weekly doses. After your 4th dose, or 30 days after you first used the pen, whichever comes first, put the pen in your sharps bin too, even if some medicine is left in it. Never try to use the leftover medicine.
3. Seal it at about three-quarters full, not right to the top.
4. Arrange disposal. When your bin is full, seal it and arrange disposal through your GP practice or your local council's sharps collection service. Many councils collect clinical waste from home, some free of charge, check your council's website.

Never decant sharps into a plastic bottle or food container. If a bin isn't available yet, keep used pens somewhere safe and out of reach of children until you have one.

Travelling with pens and needles

You can take pens and needles through airport security in hand luggage. Carry them in the original packaging with the pharmacy label attached, and bring a copy of your prescription or a letter from your pharmacy. Don't put them in the hold, the temperature isn't controlled and freezing damages the medicine. See our full guide to storing Mounjaro at home and while travelling.