Mounjaro pen needles: which fit, how to get them and when to change

Mounjaro pen needles do not come in the box. The UK Instructions for Use for the KwikPen and the SmPC both say so: “Needles are not included in the pack.” This guide gathers what the pen’s own documents say about needles, with NHS and GOV.UK material on length, gauge, prescriptions and sharps bins. Mounjaro (tirzepatide) is a prescription-only medicine; a prescriber decides whether it suits you, and this is information, not medical advice.

Mounjaro pen needles are not in the pack

The Instructions for Use label the needle diagram “Pen Needle Parts (Needles Not Included)” and later add: “Needles are not included in the pack. Check with your doctor, pharmacist, or nurse on the appropriate needle to use with your Mounjaro KwikPen.” Section 6.5 of the SmPC ends with the first of those sentences. The patient leaflet does not cover needles and sends you to the Instructions for Use, whose “Supplies needed” list adds a swab, gauze or a cotton ball, and a “sharps disposal container or household container”.

Which needles fit the Mounjaro KwikPen?

The supplies list names a “KwikPen compatible pen needle (If you do not know what pen needle to use, talk to your healthcare professional)”. It names no brand, length or gauge, so this guide names none either. Two details help: step 5 has you “push the capped pen needle straight onto the pen and twist the pen needle on until it is tight”, a twist-on fitting, and the parts diagram labels the needle’s outer shield, inner shield and paper tab. Which to use is the pharmacist’s or prescriber’s call; our KwikPen guide covers the attachment steps.

Needle length and gauge: North East London NHS guidance

The Instructions for Use are silent on size. North East London NHS guidance on pen needles for insulin and GLP-1 pens explains the two numbers: lengths run from 4 mm to 12 mm, and gauge is thickness, “the lower the gauge number the thicker the needle”, so a 29-gauge needle is thicker than a 32-gauge one. It passes on advice from FIT UK (the Forum for Injection Technique UK) that shorter, higher-gauge needles minimise pain, and says 4 mm needles “inserted perpendicularly at 90 degrees are considered to be the safest pen needle for subcutaneous injection for adults and children regardless of age, gender and Body Mass Index”, though extremely thin adults (BMI under 19) should lift a skin fold and insert the needle into it. The guidance is local and does not name Mounjaro. Our injection sites guide covers where the needle goes.

A new needle for every injection, and never share

Step 4 is unambiguous: “Select a new pen needle. Always use a new pen needle for each injection to help prevent infections and blocked needles.” The North East London guidance agrees: “All pen needles are for single use only.” Sharing is ruled out on the first page: “Do not share your Mounjaro KwikPen with other people, even if the pen needle has been changed. You may give other people a serious infection or get a serious infection from them.”

Attach just before, remove straight after

The needle goes on inside the “Preparing to inject” sequence, between wiping the red inner seal (step 3) and priming (steps 7 to 9). It comes off straight after the dose: step 15, carefully replace the outer needle shield; step 16, unscrew the capped needle into a sharps container, because “Do not store the pen with the needle attached to prevent leaking, blocking the needle, and air from entering the pen.” Our air bubbles guide explains what priming does about air.

If a needle bends or blocks

Bent needles get no mention in the Instructions for Use. Blocked ones do: a dose knob that is hard to push may mean a blocked needle, and the answer is a new needle and fresh priming. A bent or damaged needle is still a sharp, so it goes in the sharps bin and a new one goes on. Our pen not working guide takes each pen fault in turn; the how-to-inject page covers the weekly routine.

How Mounjaro pen needles are obtained in the UK

The NHS says tirzepatide is “only available with a prescription, either NHS or private”. If your Mounjaro is prescribed on the NHS, pen needles can be prescribed with it: the NHS Dictionary of Medicines and Devices lists “hypodermic insulin needles for pre-filled / reusable pen injectors” as “Valid as a prescribable product” under Part IXa of the Drug Tariff, and the North East London guidance says patients who need pen needles should be prescribed a sharps container too. With a private prescription, ask the prescriber or pharmacy that supplies your pen how needles and a sharps bin are provided. The NHS says it is important to buy privately prescribed tirzepatide from a registered pharmacy, and warns that some websites sell fake weight loss medicines. Private prices vary between regulated providers.

Disposal: the sharps bin and your council

The Instructions for Use say: “Dispose of your used pen needles in a sharps disposal container right away after use, do not dispose of loose pen needles in your household waste”, and do not recycle the sharps container. The SmPC leaves disposal to “local requirements”. For collection, GOV.UK’s clinical waste page (“Available in England and Wales only”) says “some councils can collect and dispose of used syringes, drugs, pharmaceuticals and surgical waste” and “there may be a charge for this service”; the North East London guidance adds that council collection is only by prior arrangement. The Instructions for Use say to dispose of the used pen “as instructed by your healthcare professional”, so ask your doctor, pharmacist or nurse how to get a sharps bin and how it is collected where you live.

Reporting a needle problem

A needle that fails, or a pen that will not deliver its dose, can be reported to the MHRA at yellowcard.mhra.gov.uk: the Yellow Card scheme takes reports on medical devices as well as medicines, from anyone. For side effects, the patient leaflet says to talk to your doctor, pharmacist or nurse; you can also report them to the scheme directly, online or through its app. Our side effects page covers what to expect; the FAQ page covers wider questions.

Frequently asked questions

Related reading

• Mounjaro pen not working? What the leaflet says to check
• Air bubbles in a Mounjaro pen: when they matter
• How the Mounjaro KwikPen works, click by click