How to inject Mounjaro: A step-by-step guide

The Mounjaro KwikPen is a once-weekly, multi-dose injection pen containing tirzepatide. Each pen holds four fixed weekly doses. Using it correctly is important, because it ensures you get the full dose safely. This guide covers what you need, how to choose and rotate an injection site, the injection itself step by step, how to store your pen, and how to dispose of used pens and needles. 

Mounjaro weight loss injections are prescription-only, so always follow the instructions from your prescriber and the leaflet supplied with your pen. 

How to prime the Mounjaro pen 

Each Mounjaro pen contains four fixed weekly doses, and you dial up one dose at a time using the dose knob and window. Before each injection you: 

• prime the pen to clear any air and confirm it is working 

• inject the full dose 

• check the dose window returns to “0” to confirm the full dose has gone in 

Once all four doses are used, dispose of the pen. 

What you’ll need 

• Your Mounjaro pen 

• Alcohol swabs 

• Pen needles (a new one for every injection) 

• A sharps bin 

• About 5-10 minutes 

Choosing and rotating your injection site 

Mounjaro is injected into the fatty tissue just under the skin (subcutaneously). There are three suitable areas: 

• Abdomen (stomach), keeping at least 5cm away from your belly button 

• Thigh, the front of the upper leg 

• Back of the upper arm, which is usually easier if someone helps you inject the dose 

Rotate your injection site each week to reduce the risk of bruising, lumps or irritation. You can keep using the same area but move at least a finger’s width from the previous spot. 

Avoid injecting into bruised, scarred, mole-covered skin or into broken areas, and never inject into muscle or a vein. If you also inject insulin, use a separate site for it. 

There is no need to pinch the skin, as the needle is short; you can pinch it if it feels more comfortable. 

How to inject Mounjaro: step by step 

1. Prepare a clean surface 

• Clear and wipe down the surface you are using, and lay out everything you need. 

• Wash your hands thoroughly with soap and water. 

2. Check the pen 

• Take the pen from the fridge and pull the cap straight off. 

• Check the name and dose on the label match your prescription, and that the pen is in date and undamaged. 

• Check the liquid is clear and colourless to slightly yellow and free of any particles. Do not use it if it is cloudy, discoloured or frozen. 

• Wipe the red inner seal with an alcohol swab. 

3. Attach a new needle 

• Tear the paper tab off a new needle, then push it onto the pen and twist until secure. 

• Remove the outer needle cap and set it aside for later. 

• Remove the inner needle cap and put it in your household waste. 

4. Prime the pen 

Priming clears any air and confirms the pen is working. You prime before every injection, not only with a new pen. 

• Turn the dose knob until you hear two clicks and the extended line shows in the dose window. 

• Hold the pen with the needle pointing up and tap gently to move any air bubbles to the top. 

• Press the dose knob until it stops and slowly count to five. A drop of medicine should appear, and the window should read “0”. 

If no medicine appears, repeat the priming steps up to two more times. If it still does not work, fit a new needle and try once more. If there is still no drop, do not use the pen. Contact your prescriber or pharmacy. 

5. Inject the dose 

• Clean your chosen site with an alcohol swab and let it air-dry. 

• Turn the dose knob until it stops and the window reads “1”. This is your full weekly dose. 

• Insert the needle at a 90° angle, press the dose knob until it stops, and hold for five seconds. 

• Withdraw the needle and check the window reads “0”, confirming you have had the full dose. 

A drop of medicine on the needle tip is normal. If you see a pinprick of blood, press gently with cotton wool or gauze, and do not rub. 

6. Dispose of the needle and recap the pen 

• Carefully replace the outer cap over the needle. 

• Unscrew the capped needle and put it straight into your sharps bin. Never reuse a needle or put it in household waste. 

• Replace the pen cap. Never store the pen without its cap, or with a needle still attached. 

Storing your Mounjaro pen 

Keep unused pens in the fridge, at 2°C to 8°C. Once a pen is in use it can be kept below 30°C for up to 30 days, away from direct heat and sunlight. 

Do not freeze the pen, and keep it out of reach of children. If a pen has been out of the fridge for more than 30 days, dispose of it even if doses remain. 

How to dispose of used Mounjaro pens 

Safe disposal protects you and others from used needles. 

• Needles: place every used needle in a sharps bin immediately after injecting. Do not put needles in your general or recycling bin, and never reuse them. 

• The pen: once all four doses are used, replace the cap (with no needle attached) and put the pen in your sharps bin. 

• Out-of-date storage: dispose of a pen that has been out of the fridge for more than 30 days, even if it still contains doses. 

• A full sharps bin: do not put it in your household waste. Your GP surgery, or local council can tell you how to arrange collection or drop-off.