Mounjaro FAQ: the questions people actually ask before starting

Is Mounjaro the right medicine for where I am right now?

This is the central question, and it deserves a straight answer. Mounjaro is licensed for adults whose BMI sits at 30 or above, or at 27 or above if they have at least one weight-related condition, things like high blood pressure, type 2 diabetes, obstructive sleep apnoea or high cholesterol. Lower BMI thresholds can apply for some ethnic backgrounds under UK guidance, so the number on a calculator is not always the final word.

BMI alone, though, has never been the whole story. A prescriber looks at your medical history, any medicines you already take, and conditions that might make Mounjaro unsuitable. A history of medullary thyroid carcinoma or a condition called MEN2, for example, rules it out. So does current pregnancy. That assessment is exactly what the consultation is for, and at nume, a GPhC-registered Independent Prescriber reads your answers the same day you submit them. Not software. A named clinician.

If you want to explore whether you'd be eligible, the weight-loss treatments page walks through the process from there. For a broader look at what tirzepatide is and how it compares, the tirzepatide overview is worth reading first.

What should I expect in the first few weeks of treatment?

Mounjaro's 2.5 mg starting dose is a settling-in phase. Its job is to let your body acclimatise to the medicine before any therapeutic titration begins, not to produce visible results straight away. Most people's prescribers move through 4-week intervals before any dose change, though the pace is always a clinical judgement, not a rule of thumb you apply yourself.

The side effects most commonly reported in the first weeks are gastrointestinal: nausea, loose stools, constipation, indigestion and occasional vomiting. They tend to be most noticeable after starting or after a dose increase, and for most people they settle within a week or two. Eating smaller portions, avoiding very fatty meals and keeping well hydrated all help. Exactly what arrives in the post, incidentally, is a plain, unbranded box from DPD (trackable on your phone) containing the KwikPen, which pre-fills four weekly doses in one device.

The full Mounjaro guide covers storage, injection sites and what to do around missed doses in more detail. For questions specific to the 2.5 mg starting pen, the 2.5 mg page has focused answers. The NHS medicines page for tirzepatide, nhs.uk/medicines/tirzepatide, is the definitive patient-level reference for the full side-effect list and what warrants urgent medical attention.

How does Mounjaro compare with other weight-loss treatments, and does cost matter?

The honest position on clinical evidence: in the SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, tirzepatide produced greater average weight loss than semaglutide 2.4 mg over 72 weeks. That does not make it the right choice for everyone, semaglutide (Wegovy) has a longer track record, and for some people it is the more appropriate medicine clinically. Which one suits you is a conversation with a prescriber, not a league table.

On cost: private Mounjaro pricing in the UK has shifted significantly since Eli Lilly raised the list price in September 2025. Typical private prices now run roughly £149–£375 per month depending on the dose and the provider. The Lilly price increase explainer sets out what changed and why. What matters alongside any headline figure is what that price actually includes: some providers charge separately for the consultation, the prescription and delivery. Our weight-loss overview page covers how treatment pricing at nume is structured, one figure, nothing hidden.

For the 5 mg dose specifically, which is where many people land after their first pen, the 5 mg page answers the questions that come up at that stage. NICE's appraisal of tirzepatide, TA1026, is the published basis for NHS eligibility, useful reading if you are deciding between the NHS route and a private one.

What about longer-term questions: stopping, switching and what the NHS offers?

Mounjaro is not a permanent commitment with no exit. Many people stop after reaching a stable lower weight; others continue indefinitely under ongoing clinical review. Weight can return after stopping, because the underlying biology does not disappear when the medicine does, that is a documented finding from the trial programme, not a scare story. Your prescriber is the right person to discuss what stopping looks like for you specifically.

On the NHS, tirzepatide is being phased in through primary care from June 2025 onwards, with eligibility criteria that will broaden in steps over 2026 and 2027. Right now access is restricted to people with a BMI of 40 or above alongside four or more of a defined set of health conditions. Many people do not meet those criteria yet, or cannot wait. Private treatment through a regulated pharmacy is the practical alternative. To understand more about the clinical team overseeing prescriptions at nume, the prescriber profile page gives that context. If something does not appear in these FAQs, the dedicated Mounjaro FAQs page covers a wider range of questions specific to the medicine, and our contact page is there if you need to speak to someone directly.