Mounjaro mg: what each dose strength actually does

Why does Mounjaro start at 2.5 mg if higher doses do the work?

The 2.5 mg pen isn't a treatment dose in the usual sense. Its job is adjustment. Tirzepatide slows gastric emptying and changes the way appetite signals reach the brain, and both of those effects can provoke nausea, particularly in the first few weeks. Starting low gives the gut time to settle before the dose increases.

Most people spend four weeks at 2.5 mg, then move to 5 mg. The starter dose guide goes into more detail on what to expect during that opening month. The short version: don't judge the medicine by what happens in week one. The clinical evidence (including the SURMOUNT-1 trial published in the New England Journal of Medicine) was built on a population that went through this exact ramp-up, and the results reflect the full 72-week journey, not a shortcut to the top dose.

If nausea or other gastrointestinal symptoms are significant at any point, a prescriber may advise staying at the current strength for an extra four weeks rather than stepping up. That's a clinical call, not a failure. The goal is the highest dose you tolerate well, not the highest dose on the label.

What happens between 5 mg and 15 mg, how does each step change things?

Once the 2.5 mg phase is done, the remaining steps follow the same rough pattern: four weeks at the new strength, then an assessment of how things are going. The full schedule runs 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg, with each pen containing four weekly doses of that strength.

In the SURMOUNT-1 trial, meaningful weight reduction built across the titration period. By 15 mg at week 72, participants had lost on average around 20–21% of body weight. That figure comes from a specific trial population and doesn't describe what any individual will experience, individual results vary, and your prescriber will keep that context front and centre. Those considering what to expect at 5 mg can find a detailed breakdown there.

Not everyone reaches 15 mg, and there's no rule that they should. Some people do very well at 10 mg or 12.5 mg with fewer side effects. Clinical guidance recommends the lowest effective dose rather than the maximum dose. What each mg step changes, broadly, is the degree of appetite suppression and the speed of gastric emptying, and therefore both the weight-loss effect and the gastrointestinal tolerance challenge.

For anyone exploring the 5 mg pen specifically or curious about the 7.5 mg step, there are dedicated pages covering those stages in more detail.

Who is the titration schedule designed for, does the licensed eligibility change by dose?

The licensed eligibility criteria are the same across all Mounjaro strengths. Adults with a BMI of 30 or above, or a BMI of 27 or above alongside at least one weight-related condition (such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea), may be considered. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. The prescriber assesses the full clinical picture, BMI alone isn't the whole story.

NICE's appraisal of tirzepatide (TA1026) focuses on adults with a BMI of 35 or above plus at least one weight-related comorbidity for NHS access, but private prescribing follows the licensed SmPC criteria, which is broader. People who don't meet NHS thresholds or prefer not to wait for a referral can access Mounjaro through a regulated private pharmacy like nume, subject to the same clinical assessment.

The weight-loss treatment overview sets out the comparison between NHS and private routes, if that's a useful context. And the 2.5 mg page is a good starting point for anyone right at the beginning of the process.

What are the practical differences between the pens at each mg strength?

All Mounjaro strengths come in the same KwikPen format, a pre-filled, multi-dose pen delivering four weekly injections per device. The mechanism is identical; only the concentration inside changes. You'll rotate injection sites between your abdomen, thigh and upper arm each week. Storage is in the fridge at 2–8°C; the Patient Information Leaflet sets out the exact room-temperature window if you need to travel with it, and it's worth reading that section carefully rather than relying on a general rule.

When a pen is dispatched through nume, it arrives via DPD the next working day in plain, unbranded packaging, tracked to your phone, no indication of what's inside. The pen itself is compact and discreet, designed for at-home administration with a fine needle.

The guide to getting Mounjaro in the UK covers the full supply process, including what identity and weight verification looks like at the consultation stage. For the 4 mg Mounjaro question, that's not a licensed UK strength; the steps go 2.5 mg, then straight to 5 mg. Anyone who has seen a 4 mg reference can find clarification there.