4mg Mounjaro and the dose decision behind it

The doses that actually exist, and why 4mg isn't one of them

Mounjaro (tirzepatide) is available in the UK as a pre-filled KwikPen in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg. These are the only licensed presentations. There is no 4mg pen. The number 4 sometimes surfaces in discussions about unit-based dosing or overseas presentations, but for anyone receiving treatment in the UK, it has no practical meaning. If you've seen a 4mg dose mentioned on a forum or in an article, it's worth setting that aside.

The titration schedule is deliberate. Treatment opens at 2.5mg, a dose calibrated to let your body adjust to the medicine before any meaningful appetite suppression kicks in. After roughly four weeks, the prescriber typically moves you to 5mg, then steps up from there in four-weekly intervals as tolerated. The 2.5mg starting pen is sometimes mistaken for a low-efficacy dose; in reality its job is settling the system, not shifting weight, and that distinction matters for managing expectations in the first month. You can read more about what the 5mg step involves if you're approaching that transition.

The NHS tirzepatide medicines page sets out the full titration pathway and side-effect profile in plain language, and is worth bookmarking alongside the Patient Information Leaflet that comes with your pen.

What drives the decision about which dose you land on

A common misconception is that higher always means better, so patients should push for the maximum as fast as possible. That's not how it works. The goal is the lowest dose that delivers meaningful weight loss with acceptable tolerability. Some people do well at 5mg or 7.5mg and their prescriber sees no clinical reason to increase further. Others need the upper rungs. The SURMOUNT-1 trial, published in the New England Journal of Medicine, showed average weight reductions of around 20–21% at 15mg over 72 weeks, impressive figures, but they were averages across thousands of participants, not a promise tied to reaching 15mg specifically.

Side effects are the main moderator. Nausea, loose stools, reduced appetite and fatigue tend to peak after a dose increase and settle within one to two weeks for most people. If they don't settle, slowing the titration is a legitimate clinical choice, not a failure. Your prescriber makes that call based on what you report, which is precisely why the aftercare conversation matters as much as the initial prescription.

At nume, every repeat order is reviewed by a GPhC-registered prescriber before dispatch. Nobody increases your dose automatically.

How this connects to the 4mg question people are really asking

When someone searches for 4mg Mounjaro, they're usually at one of two points: they've just started on 2.5mg and are wondering what comes next, or they've seen a reference to 4mg that confused them about the UK schedule. Either way, the practical answer is the same. The next licensed step after the starter pen is 5mg, and it's the first dose where most people begin to notice a meaningful shift in appetite. From there, the 7.5mg pen is the next rung, continuing in 2.5mg increments up to the 15mg maximum.

If you're trying to make sense of the full dose range before speaking to a prescriber, the Mounjaro dose guide covers all six strengths and what each stage of titration involves. For context on cost as your treatment progresses and doses change, the Mounjaro cost page gives an honest picture of how UK private pricing is structured.

NICE's appraisal of tirzepatide, TA1026, confirmed the clinical evidence base that supports the licensed UK schedule. It's worth reading if you want to understand the criteria behind NHS-side access too.

The route to starting or adjusting treatment

Mounjaro is a prescription-only medicine. No online reading, including this page, substitutes for a clinical assessment. What a prescriber considers before prescribing or titrating includes your current weight and BMI, relevant medical history, any medicines you already take, and how you've tolerated treatment so far. The four-dose pen format means each pen lasts four weeks (one injection per week) and the titration decision typically coincides with ordering the next pen.

If you're ready to begin that conversation, speak to our prescribers through a free consultation. A real clinician reads your answers the same day, no algorithm, no queue.