Mounjaro FAQs: the questions our prescribers hear every week

What makes Mounjaro different from other weight-loss injections?

Most weight-loss injections work on a single pathway: the GLP-1 receptor, which slows gastric emptying and reduces appetite. Mounjaro targets that receptor too, but it also activates the GIP receptor, a second gut hormone involved in energy balance and blood-sugar regulation. No other weight-loss medicine currently licensed in the UK does both. According to the NHS tirzepatide medicine guide, this dual action is why tirzepatide behaves differently from semaglutide-based treatments, even though the practical experience of injecting once a week and managing a slow titration schedule looks similar from the outside.

The SURMOUNT-1 trial, which randomised 2,539 adults with obesity and without diabetes over 72 weeks, reported average body-weight reductions of around 20–21% at the 15 mg dose. NICE cited that evidence directly when issuing its recommendation. For context, that is a meaningful step beyond the approximately 15% average seen with semaglutide 2.4 mg in the STEP 1 trial. Head-to-head data from SURMOUNT-5 (published in the New England Journal of Medicine in 2025) confirmed tirzepatide produced greater average weight loss than semaglutide 2.4 mg over 72 weeks.

None of this means Mounjaro is right for every person. The biology that produces those averages plays out differently in individuals, and a prescriber's job is to look at your specific picture (not a trial statistic) before recommending treatment. If you would like a thorough grounding in how the medicine works before speaking to a prescriber, our Mounjaro page covers the mechanism, the evidence and the UK licensing picture in plain language. Results from the NICE tirzepatide appraisal (TA1026) are the benchmark, but they are not a promise for any one patient.

Who can get Mounjaro on the NHS, and who typically uses the private route?

The NHS rollout of tirzepatide is phased. From around June 2025, adults with a BMI of 40 or above plus four or more qualifying weight-related conditions (which include high blood pressure, dyslipidaemia, obstructive sleep apnoea, cardiovascular disease and type 2 diabetes) became eligible. A second cohort (BMI 35–39.9 with four or more of those conditions) was activated in June 2026. Further phases are expected through 2027. Lower BMI thresholds apply for South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds throughout.

In practice, many people find they either do not yet meet the NHS criteria, or they do meet them but face a significant wait through their local service. The private route, through a regulated pharmacy such as nume, offers an alternative: no referral needed, no waiting list, and a clinical assessment that is completed the same day. It is worth reading about what private Mounjaro treatment actually costs before making any decisions, because the price varies by dose and what it includes differs between providers.

GP practices may also prescribe tirzepatide under the 2026/27 QOF arrangements, though participation is optional and varies by area. If you are unsure whether you qualify through the NHS, your GP is the right first call.

What side effects should you know about before starting?

The most common side effects are gastrointestinal: nausea, loose stools, constipation, indigestion and burping. Fatigue and headache are also reported. Most people find these are at their worst in the days after starting the 2.5 mg pen or moving up to the next dose, then settle within a week or two as the body adjusts. That is one reason the starting dose is set low, the 2.5 mg pen's job is to let your system adapt, not to produce the full therapeutic effect straight away. If you want detail on specific strengths, our page on the Mounjaro 2.5 mg starter pen covers what to expect at that early stage of treatment, and the 5 mg pen page covers what to expect at that stage of treatment.

A small number of people experience more serious effects. In January 2026, the MHRA issued a Drug Safety Update for GLP-1 medicines specifically highlighting acute pancreatitis: severe, persistent stomach pain that may spread to the back, with or without vomiting, warrants urgent medical assessment. Gallbladder problems, signs of a serious allergic reaction, and significant dehydration from repeated vomiting should also prompt prompt contact with a healthcare professional.

People using oral contraceptives should know that tirzepatide may reduce pill absorption during the first four weeks of treatment and for four weeks after each dose increase, adding a non-oral method during those windows is the standard NHS advice. Always discuss any medicines you take regularly with your prescriber before starting. Side effects and interactions can also be reported directly at the MHRA Yellow Card scheme, something our clinical team actively encourages.

How does the consultation and prescription process work in practice?

At nume, the process is built around a single principle: a real clinician reviews your answers, not an automated decision engine. You complete a free consultation online; a GPhC-registered Independent Prescriber reads it the same day. There is photo-ID verification and a live weight check on video, so the clinical picture is accurate before any prescription is written. If you order before midday on a working day and are approved, your treatment is dispatched the same day and arrives with DPD the next working day, in plain packaging, a detail that matters to a lot of people. There is one transparent price covering consultation, prescription, the medicine itself and delivery, with no subscription attached.

Every repeat order goes through the same clinical review, not a rubber stamp, an actual check that treatment is still appropriate and progressing well. If you are transferring from another provider or requesting a dose above the starter pen, you will be asked to provide evidence of your current treatment. This is standard across reputable services and exists to protect you.

For a broader overview of tirzepatide as a medicine, the tirzepatide information page covers the mechanism, the trial evidence and the UK licensing picture in more detail. And if you have further questions that the above has not covered, our Mounjaro FAQ page addresses common queries about the medicine, dosing and what to expect from treatment, while the nume general FAQs address common service and process queries.