GP weight loss injections: how they work and how to access them

What does a GP actually do when prescribing weight loss injections?

A GP's role in prescribing weight loss injections from a GP is the same as any prescriber's: they assess whether the medicine is clinically appropriate for you specifically. That means reviewing your BMI, any existing health conditions, your current medicines, and whether there are contraindications, such as a personal or family history of medullary thyroid cancer, a history of pancreatitis, or certain gastrointestinal conditions. They will also discuss realistic expectations. Neither Mounjaro nor Wegovy is assessed for quick or cosmetic weight loss; the MHRA's published guidance on GLP-1 medicines makes this point explicitly.

If your GP decides the treatment is suitable, they write a prescription. On the NHS, that prescription is dispensed under the terms of whichever commissioning arrangement your area operates. In a private setting, you pay separately for the consultation, prescription, and medicine. One thing worth knowing: a GP does not have to prescribe these medicines, and many practices have not yet opted into the NHS tirzepatide pathway that opened to primary care in April 2026. So a referral to a weight management service, or a private route, may still be the practical answer even where a GP is supportive.

The clinical assessment itself (checking your weight, your history, your suitability) is what makes a prescription legal and safe. Whether a GP can give weight loss injections depends on their service setup, not just their willingness.

Who qualifies for weight loss injections on the NHS versus privately?

The NHS pathway for these medicines is currently rationed by strict eligibility criteria, rolled out in phases. From June 2025, tirzepatide (Mounjaro) became available on the NHS to adults with a BMI of 40 or above who have four or more of five specified weight-related conditions: high blood pressure, dyslipidaemia, obstructive sleep apnoea, cardiovascular disease, and type 2 diabetes. A second cohort (BMI 35 to 39.9 with four or more of those conditions) opened in late June 2026. NICE's recommendation for tirzepatide (TA1026) sets out these thresholds in full, including the lower BMI cut-offs that apply for some ethnic backgrounds under UK guidance.

Wegovy (semaglutide) on the NHS requires referral to a specialist weight management service and carries a two-year maximum treatment duration under NICE's appraisal (TA875). Waiting lists for those services are commonly long. If you meet neither set of NHS criteria, or you do not want to wait, a private prescription is the lawful alternative, subject to a clinical assessment confirming you meet the licensed criteria. You can read about getting weight loss injections without a GP referral if you want to understand the private route in detail.

Lower BMI thresholds apply for certain ethnic backgrounds across both medicines and both pathways; the adjustment is 2.5 kg/m² under UK guidance. BMI alone is never the whole picture, the prescriber weighs up all of it.

What side effects do GP weight loss injections cause?

The most common side effects of both Mounjaro and Wegovy are gastrointestinal. Patients frequently report nausea, loose stools, constipation, indigestion, or burping, particularly during the early weeks or following a dose increase. Fatigue and headache are also reported. The NHS tirzepatide medicines page lists these in plain language alongside guidance on when to seek help.

Most GI symptoms settle within a couple of weeks as your body adjusts. Keeping well hydrated matters, especially if nausea reduces your appetite for fluids. Eating smaller, lower-fat meals at the start can help too, though specific advice should come from your prescriber rather than general reading.

There are rarer but serious effects to be aware of. The MHRA issued a Drug Safety Update in January 2026 specifically highlighting acute pancreatitis as an infrequent but potentially serious side effect of GLP-1 medicines: severe, persistent stomach pain (particularly if it radiates to the back, with or without vomiting) warrants urgent medical attention. Gallbladder symptoms, signs of dehydration from prolonged vomiting or diarrhoea, and allergic reactions are other reasons to get medical help promptly rather than waiting for a scheduled review. Suspected side effects can be reported via the MHRA Yellow Card scheme. Your Patient Information Leaflet remains the authoritative reference for the full side-effect profile of whichever medicine you are prescribed.

How does a private prescription route compare to going through your GP?

The practical difference between a private online prescriber and a GP comes down to speed, eligibility thresholds, and what the service includes. A GPhC-registered online pharmacy can assess you the same day and, where clinically suitable, dispatch your medicine that day for next-working-day delivery. GP access depends on whether your practice has opted into the relevant NHS contract and whether you meet the NHS eligibility criteria, which are considerably narrower than the licensed thresholds.

Private treatment costs more than an NHS prescription, but it is inclusive of things that are often charged separately elsewhere: consultation, clinical review, the prescription itself, delivery, and ongoing aftercare support. If you are based locally, our page covering weight loss injections in Benfleet explains what to expect from a nearby private service. Cost considerations are real, and if you are weighing up your options it is also worth reading about the three weight loss injections currently available so you understand how Mounjaro, Wegovy, and their alternatives compare before committing to a route.

Any legitimate private provider should be verifiable on the GPhC register at pharmacyregulation.org. That check takes under a minute and is worth doing before submitting any consultation. Red flags include sellers offering these medicines without a clinical assessment, or prices that sit well below the market range without explanation.

Our clinical team at nume (reviewed by a GPhC-registered Independent Prescriber) assesses every consultation personally. If you have questions ahead of starting, our FAQs page covers the most common ones.