How to Inject Mounjaro the First Time: A Calm Step-by-Step

If you're wondering how to inject Mounjaro the first time, take a breath: it's more straightforward than it looks. The pen is designed to do most of the work for you, and once you've done it once, the routine becomes second nature. This guide walks you through it calmly, from taking the pen out of the fridge to putting the used pen safely away.

Mounjaro (tirzepatide) is a prescription-only medicine, and a prescriber decides whether it's suitable for you. This article is information only, not medical advice. Always follow the instructions that come with your specific pen and anything your prescriber or pharmacist has told you.

Before you start: what you'll need

Set yourself up somewhere calm with good light. Gather:

• Your Mounjaro KwikPen (check it's the correct dose — the starter dose is usually 2.5 mg)
• A new KwikPen-compatible pen needle — needles are not included in the pack, so ask your pharmacist which to use
• A swab, and gauze or cotton wool
• A sharps bin for safe disposal

Check the label and the expiry date. Look at the medicine in the pen: it should be clear and colourless to slightly yellow. If it's cloudy, discoloured or has particles, don't use it — speak to your pharmacist.

Storage before and after first use

Unused pens are kept in the fridge at 2°C to 8°C and must never be frozen; don't use a pen that has been frozen. Once you've started a pen, it can be kept out of the fridge at up to 30°C, away from heat, for up to 30 days, and then it must be thrown away. For more on keeping it at the right temperature, our how-to-inject guide covers storage in detail.

How to inject Mounjaro the first time, step by step

In the UK, Mounjaro comes as the KwikPen: a pre-filled pen that holds four weekly doses, with a new pen needle attached for each injection. The Instructions for Use in your pack are the version to follow; in outline, the routine is:

1. Wash your hands with soap and water.
2. Pull the pen cap straight off and check the pen: the right medicine and strength, in date and not damaged.
3. Attach a new pen needle. Wipe the red inner seal with a swab, push the capped needle straight onto the pen and twist until tight, then pull off the outer needle shield (keep it) and the inner needle shield.
4. Prime the pen. Turn the dose knob until you hear 2 clicks, hold the pen needle-up and tap it gently to bring air bubbles to the top, then push the dose knob in until it stops and slowly count to 5. A little medicine should appear at the needle tip; this goes into the air, not into your body.
5. Choose your injection site (more on where below).
6. Dial and inject. Turn the dose knob until it stops to select the full dose, insert the needle into your skin, then push the dose knob in until it stops and slowly count to 5 while holding it before you remove the needle.
7. Pull the needle out. A drop of medicine on the needle tip is normal. If you see blood, press lightly with gauze or cotton wool. Don't rub the area.
8. Tidy away. Carefully replace the outer needle shield, unscrew the needle and put it straight into your sharps bin, then put the pen cap back on. Never store the pen with a needle attached.

That's it until next week. Each KwikPen holds four weekly doses: throw the pen away after the fourth dose, or 30 days after you first used it, whichever comes first.

Where to inject: choosing and rotating sites

Mounjaro goes into the fatty layer just under the skin (a subcutaneous injection). The approved areas are:

• Your tummy (abdomen) — keep at least 5 cm away from your belly button
• Your thigh — the front, fleshy part
• Your upper arm — the back, and the leaflet says someone else should give the injection there

Many people find the tummy the easiest and least sensitive spot for a first go. Rotate the exact point each week to avoid lumpy or hardened skin. If you always use your tummy, that's fine — just move to a different patch a few centimetres away each time. Avoid skin that's bruised, sore, red, hard or scarred. Our guide to Mounjaro injection sites covers rotation in more detail.

Which day and what dose?

Mounjaro is a once-weekly injection. Pick a day that suits your routine and stick to it. You can inject at any time of day, with or without food. If you need to, you can change your regular day as long as your last dose was at least three days (72 hours) earlier.

Treatment starts low and builds up slowly to help your body adjust and reduce side effects. The usual pattern is 2.5 mg weekly for four weeks — a starter dose, not a treatment dose — then 5 mg, with further increases in 2.5 mg steps no sooner than every four weeks, up to a maximum of 15 mg. Your prescriber tailors your maintenance dose to you. Our dosage page explains the schedule in full.

Nerves are normal — a few calming tips

Feeling anxious before the first injection is completely usual. A few things help:

• Sit or lie somewhere comfortable so you're not tensing up.
• Relax the part of your body you're injecting into — soft, unclenched skin is more comfortable.
• Look away as the needle goes in if that helps, then slowly count to 5 while you hold the dose knob in.
• Have everything ready before you uncap, so there's no scrambling.

If the idea still feels overwhelming, ask your pharmacist or clinic nurse to talk you through it, or watch the manufacturer's demonstration. There's no prize for rushing.

Disposing of your pen safely

Put each used needle straight into a sharps bin — never loose in your household rubbish — and don't recycle the bin. When a pen is finished, dispose of it as your pharmacist or prescriber advises. When the bin is full, your local council or pharmacy can advise on disposal; arrangements vary by area. Keep pens and sharps bins well away from children and pets.

What to expect afterwards

The most common side effects are digestive: nausea, diarrhoea, constipation, vomiting and tiredness. These tend to be worse when you start or increase a dose and usually ease over time. Eating smaller, plainer meals and sipping fluids can help. Our side effects guide goes into more detail.

Rarer but more serious problems include pancreatitis, gallstones and dehydration that strains the kidneys. Stop using it and seek urgent medical help for severe, persistent tummy pain, with or without nausea and vomiting, as this can be a sign of pancreatitis. Get medical advice for ongoing vomiting or signs of dehydration. You can report any suspected side effect through the MHRA Yellow Card scheme, which helps monitor medicine safety across the UK.

Frequently asked questions