How often do you inject Mounjaro for weight loss?

Step 1, Pick your day and keep it

The weekly rhythm is the foundation of Mounjaro treatment. You inject once every seven days, and the specific day you choose at the start tends to stay the same for the life of your prescription. Monday, Saturday, any day that fits, the clinical requirement is consistency, not the day itself. Some people anchor it to something routine: injecting on a Sunday evening because the pen lives in the fridge door alongside the meal-prep for the week. Others tie it to a midweek gym session. Either way, a locked-in day makes it much less likely you'll drift.

If you do inject a day early or late by accident, the NHS advises checking the Patient Information Leaflet that comes with your pen for what to do, and, if in doubt, speaking to your prescriber. What not to do is double up on doses to compensate. If you want to understand how often you inject Mounjaro and what to do if your timing slips, your prescriber can cover the missed-dose question in more detail.

Mounjaro is a prescription-only medicine (POM). Every person who receives it through a regulated pharmacy, including through nume's Mounjaro service, has had their suitability assessed by a qualified prescriber before a single pen is dispensed.

Step 2, Start at 2.5 mg and let the dose lead

The first four weeks use the 2.5 mg dose. That starting dose exists for one reason: to give your digestive system time to adapt. Nausea, mild indigestion and occasional loose stools are common in the early weeks, and beginning low keeps those effects manageable for most people. It is not a therapeutic dose in the sense of producing significant weight loss, its job is adjustment.

After four weeks on 2.5 mg, the prescriber typically moves the dose to 5 mg for the next four-week block. From there, steps may continue through 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg, each step at roughly four-week intervals. The word "may" matters here. Not everyone moves through every step; some people tolerate lower doses well and see good results before reaching the higher end of the scale. Others move more slowly if side effects are noticeable at a particular step. The prescriber makes that call based on your response and tolerance, as outlined in NICE's appraisal of tirzepatide (TA1026).

Six UK strengths are available: 2.5, 5, 7.5, 10, 12.5 and 15 mg. The pen itself contains four weekly doses, so one pen lasts approximately one month at any given dose level. For more on how the full process works in practice, using Mounjaro for weight loss walks through the practical steps.

Step 3, The injection itself

Each injection is subcutaneous, meaning it goes into fatty tissue just beneath the skin rather than into muscle or a vein. The three approved sites are the abdomen (avoiding the area around the navel), the front of the thigh, or the upper arm. Rotating between sites (and between spots within a site) reduces the chance of skin irritation or hardening at one spot over time. A guide to where to inject Mounjaro covers rotation and technique in full.

The KwikPen is pre-filled and pre-set to the correct dose. Most people find the injection itself takes a matter of seconds. Cleaning the skin beforehand with an alcohol swab is straightforward, and the used needle should go directly into a sharps container rather than the household bin.

Storage matters too. The pen is kept refrigerated between 2°C and 8°C, and the exact rules for using it at room temperature are in the Patient Information Leaflet, always check there, not here, for that detail. Once you understand the injection routine, how to take Mounjaro for weight loss is a useful reference if you want the full picture on dosing, timing and technique before the weekly habit settles. Most patients find it feels unremarkable within a month.

What the once-weekly schedule means for results

Tirzepatide works by activating two gut-hormone receptors (GIP and GLP-1) that are involved in appetite signalling and blood-sugar regulation. The once-weekly dosing maintains a steady level of the medicine in your system rather than sharp peaks and troughs, which is part of why the schedule is so consistent.

In the SURMOUNT-1 clinical trial, involving thousands of adults with obesity, participants on the 15 mg dose saw an average body-weight reduction of around 20–21% over 72 weeks alongside a reduced-calorie diet and increased physical activity. Results varied between individuals; these are averages from a clinical-trial population, and your own outcome depends on many factors your prescriber will discuss with you.

Thinking about what Mounjaro costs as a private treatment? A UK price comparison for Mounjaro sets out the market context honestly. For a broader look at weight-loss treatment options, that page covers how the different medicines and approaches compare. When you're ready to find out whether Mounjaro is clinically suitable for you, our prescribers are available the same day, start your free consultation and a real clinician, not an automated system, will review your answers.