Your practical Mounjaro user guide: from first injection to ongoing treatment

Step 1, Storing the pen and preparing for your injection

Mounjaro KwikPens live in the fridge. A sensible spot is the fridge door shelf, away from the freezer compartment; freezing the pen damages it and it should not be used if frozen. Before your scheduled injection, take the pen out and let it reach room temperature for around 30 minutes, injecting straight from the cold can increase discomfort at the site. If you need to travel with a pen, refer to the Patient Information Leaflet for the permitted room-temperature storage window; the exact number of days matters and the leaflet is the definitive source.

Check the pen before every use. The liquid should be clear to slightly yellow and free from particles. Check the expiry date printed on the label. If anything looks wrong (cloudiness, visible particles, an expired date) do not inject and contact your prescriber. More detail on what to look for is covered in the full Mounjaro guide for patients new to the pen.

Wash your hands thoroughly before handling the pen. The injection sites are the abdomen (at least 5 cm from the navel), the front of the thigh, or the outer upper arm. Rotate the exact location each week, using the same spot repeatedly can cause localised tissue changes that slow absorption. Clean the skin with an alcohol swab and let it dry before injecting.

Step 2, Injecting correctly and what to do immediately after

Mounjaro's KwikPen is a multi-dose device. Remove the base cap, press the pen firmly against the skin at a 90-degree angle, then press and hold the injection button until you hear a click and the number in the dose counter changes. Hold for a further ten seconds before removing the pen, this ensures the full dose is delivered. Do not rub the site afterwards.

Replace the base cap. Each pen contains four doses, so you will use the same pen for four consecutive weekly injections before starting a new one. Discard used pens safely, a sharps container is the correct disposal method; do not place capped pens in household bins. Your local pharmacy or GP surgery can advise on collection points.

Record the day you inject. Most people settle on a fixed weekly day that fits their routine. If you have any questions about what happens if a dose is delayed or missed, your prescriber and the Patient Information Leaflet are the right places to go, and our tirzepatide dosing guide also explains how the schedule works in practice, though titration timing and missed-dose decisions sit firmly with the clinical team, not with general guidance.

Step 3, Dose increases and what to expect as treatment progresses

The prescriber-led titration schedule moves through 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg and 15 mg, typically in monthly steps, though the pace depends on how well you are tolerating each level. The NICE appraisal of tirzepatide notes that if a patient achieves less than 5% weight loss after six months at the highest tolerated dose, continuing treatment should be reviewed, it is worth understanding this benchmark from the outset. You can read the NICE guidance on Mounjaro to understand the evidence basis behind these recommendations.

Gastrointestinal effects (nausea, loose stools, constipation, reflux) tend to be at their most noticeable in the first week or two after a dose increase, then settle for most people. Eating smaller meals, avoiding very fatty food and staying well hydrated all help. If symptoms are severe or persistent, contact your prescriber before the next scheduled dose; reducing to the previous dose level is sometimes the right call and is a clinical decision, not something to manage alone.

For a sense of what typical results look like across the clinical programme, the evidence behind tirzepatide's effectiveness pulls together the trial data in plain language, including the SURMOUNT-1 figures published in the New England Journal of Medicine. Weight loss is meaningful for many people, but individual responses vary and are not guaranteed.

Step 4, Monitoring your health and knowing when to get help

Most people using Mounjaro do so uneventfully, but there are symptoms that require prompt medical attention. In January 2026 the MHRA issued a Drug Safety Update specifically highlighting acute pancreatitis as a known, serious side effect of GLP-1 medicines: if you develop severe stomach pain that radiates to the back, with or without vomiting, stop injecting and seek urgent medical attention. Do not wait to see if it improves. Details are on the MHRA's Yellow Card reporting site, where you can also report any suspected side effect.

Other symptoms worth calling a doctor about rather than waiting: signs of a serious allergic reaction (swelling, difficulty breathing, rash), symptoms of gallbladder problems (severe pain under the right ribcage), or significant dehydration following a bout of vomiting or diarrhoea. Women using oral contraceptives should be aware that the NHS advises adding a barrier method for the first four weeks of treatment and for four weeks after each dose increase, because gastrointestinal slowing can affect pill absorption, and this and other practical considerations are covered in our tirzepatide guide for anyone who wants a broader overview of the medicine.

Your prescriber reviews your treatment before every repeat at nume. If you have questions between orders, our support team is available seven days a week, and your prescriber can be reached through the aftercare pathway. This ongoing oversight (a prescriber, not an algorithm, reading your notes each time) is one of the things that separates regulated private care from simply buying a product, and it is reflected in the experiences shared by Mounjaro users who have gone through the same process. If you are deciding whether private treatment is the right route, the free consultation is the sensible first step.