How to take your Mounjaro shot, step by step

Step 1, Get everything ready before you uncap the pen

Good preparation takes thirty seconds and makes the injection itself considerably easier. Take your pen out of the fridge and set it on a clean, flat surface. Give it ten to fifteen minutes to reach something close to room temperature; injecting cold medicine is a common cause of the stinging people notice and is entirely avoidable. While you are waiting, wash your hands thoroughly with soap and water. Then gather what you need: your Mounjaro KwikPen, a clean alcohol swab, and a sharps disposal bin within easy reach. UK law requires used pens to go directly into an approved sharps container, not into your household bin.

Before you do anything else, look at the medicine through the pen window. It should be clear or very slightly yellow and free from particles. If it looks cloudy, discoloured, or contains floating matter, do not use that dose and contact your prescriber or our support team. Check the label confirms the correct strength and that the pen is within its use-by date.

Once you are satisfied, choose your injection site for this week. The three licensed options are the lower abdomen (at least five centimetres from your navel), the front of your thigh, or the outer upper arm. More detail on choosing the right spot and why rotation matters is covered in our guide to where to take your Mounjaro shot. Wipe the chosen area with an alcohol swab and allow the skin to dry fully, injecting through wet skin can sting.

Step 2, Using the KwikPen: the injection itself

The Mounjaro KwikPen is designed to be straightforward. Remove the base cap (you will hear a click) and check the pen is set to the correct position for an injection (your patient information leaflet shows exactly what to look for). Press the pen flat and firmly against the skin of your prepared injection site; do not pinch the skin unless you have very little subcutaneous tissue at that location. Press and hold the injection button. You will hear a first click when the injection starts and a second click when it is complete. Keep the pen pressed against the skin for at least ten seconds after that second click before removing it, this ensures the full dose is delivered.

A question our prescribers hear most weeks is whether the pen should be held at an angle. The KwikPen is designed for a straight 90-degree approach against the skin, not an angled one. If you find the auto-needle intimidating at first, that feeling tends to settle after the first couple of injections; the needle itself is short and fine.

After removing the pen, a small amount of redness or a slight raised spot at the site is common and typically fades within a few hours. Do not rub the area. Place the used pen directly into your sharps container. For a closer look at how the pen mechanism works, our page on how to use your Mounjaro pen covers the device in more detail.

Step 3, After the injection: what to watch for and when to act

Most people tolerate Mounjaro well, particularly on the lower starting doses. The side effects most often reported are gastrointestinal: nausea, loose stools, constipation, or a feeling of fullness that lingers longer than usual. These tend to be most noticeable after your first injection or after stepping up to a higher dose, and they generally ease over one to two weeks as your body adjusts. Eating smaller portions and avoiding very fatty meals on injection day can reduce the likelihood of nausea, something many patients find helpful once they know about it. If you are switching from a different GLP-1 or are new to weekly injections altogether, our guide on how to take a tirzepatide shot walks through the full process in plain terms.

A small number of people experience more significant symptoms. In January 2026, the MHRA issued a Drug Safety Update for GLP-1 medicines reminding prescribers and patients that acute pancreatitis, while infrequent, can occur: get urgent medical attention for severe stomach pain that spreads to your back, especially if it comes with vomiting. Signs of an allergic reaction (widespread rash, swelling of the face or throat, difficulty breathing) also need emergency care.

For anything that is concerning but not an emergency, our FAQs cover common questions, and our aftercare team is available seven days a week. Any suspected side effect can also be reported directly through the MHRA Yellow Card scheme. Missed dose, timing questions, or decisions about your next dose increase should always go through your prescriber, not general advice online.

Keeping your pen safe between doses

Each KwikPen holds four weekly doses. In the days between injections it lives in the fridge, between 2°C and 8°C, away from the freezer compartment and direct light. If you are travelling or the pen is out of the fridge for any reason, refer to the patient information leaflet for the specific time window that applies, overstating or understating that figure in general content would be misleading, and the leaflet's figures are the ones your prescriber and pharmacist stand behind.

The Mounjaro injection overview page covers storage and travel questions in more depth. For the broader picture of how tirzepatide works and what the clinical evidence shows, the Mounjaro treatment page is the natural next read. If you are weighing up costs as part of your decision, a clear breakdown of what private treatment typically involves is on our Mounjaro prices page.

If you are not yet a patient and are considering starting treatment, speak to our prescribers through a free consultation. A real clinician reads every submission the same day and will discuss whether tirzepatide is the right fit for your health picture.