About 1.6 million people in the UK are currently on weight-loss drugs, with most buying them privately rather than through the NHS. The most popular jabs are Mounjaro and Wegovy - injectable pens or capsules that work by mimicking the hormone GLP-1 to suppress appetite. Mounjaro also tinkers with metabolism and energy balance, because apparently one hormonal impersonation isn't enough.
These drugs are highly effective, but experts are now warning users about the risk of weight gain once they stop. A January 2026 study in the British Medical Journal found that people who came off weight-loss injections regained their lost pounds four times more quickly than those who stopped conventional dieting and exercise. Normal food cravings return with a vengeance, it seems.
The first head-to-head trial of Mounjaro and Wegovy - funded by Mounjaro manufacturer Eli Lilly - involved 750 obese people with an average weight of 113kg (nearly 18 stone). After 72 weeks, Mounjaro patients achieved a 20% weight reduction, beating Wegovy's 14%. A separate May 2026 study in Nature Medicine, also funded by Eli Lilly, found that patients who took a daily tablet called orforglipron avoided regaining much of the weight they had lost. The drug is already available in the US and could soon launch in the UK, though more research is needed to determine if patients might need to take it for the rest of their lives.
NHS access is limited. Wegovy is available in England, Wales and Scotland for adults with a BMI of at least 35 and at least one weight-related health condition, or people with cardiovascular disease who are overweight. It's prescribed for a maximum of two years, alongside a diet and exercise programme. Mounjaro has been available from specialist NHS weight-loss clinics in England and Wales since March 2025, and from some GPs in England since June 2025 under strict criteria. Around 3.4 million people could eventually qualify, but NICE warns it could take over a decade to roll out access to everyone.
For those going private - an estimated nine in 10 users - pens cost between £100 and £300 per dose, available in supermarkets, chemists and high-street clinics. Since February 2025, online pharmacies must verify BMI via questionnaires or photos to prevent healthy-weight individuals or those with eating disorder histories from buying the jabs. A tablet version of Wegovy has also been approved by the MHRA for private prescription, though pricing is unclear (the US starting dose was about £110 a month).
Common side-effects include nausea, vomiting, bloating, constipation and diarrhoea - the usual party tricks. Rare serious side-effects can include gallbladder and kidney problems, depression, and unconfirmed pancreas issues. The MHRA warns women that the drugs must not be taken during pregnancy due to lack of data on effects on unborn children, and they can interfere with contraceptive pill absorption, so alternative contraception is recommended.