Britons warned of 'very common' side effects as weight loss drug sees mass NHS rollout - including nausea and vomiting

Around 220,000 people with the greatest need are expected to receive Mounjaro (also known as tirzepatide) over the next three years. The drug works by lowering blood sugar levels and slowing down how quickly food is digested.

However, those considering this weight loss strategy should note that "very common" side effects include gastrointestinal issues such as nausea, vomiting, diarrhoea, and constipation, warned Boots Online Doctor.

These symptoms mainly occur with dose increases and tend to settle with time, but patients should be prepared to manage these discomforts as their body adjusts to the treatment.

Other common side effects could include fatigue, feeling lightheaded, excess wind, gallstones, gastroesophageal reflux, injection site reactions, hair loss and hypoglycemia in patients with type 2 diabetes.

To manage these symptoms, patients should inject themselves at the same time and day each week to maintain regular intervals between doses.

Staying hydrated by sipping water and clear liquids can also help with nausea, vomiting or diarrhoea.

Eating smaller, more frequent meals and avoiding strong smells or tastes may also provide relief. For constipation, increasing fibre intake, staying well hydrated and eating small fruits such as prunes, figs, or grapes can help.

Regular activity, like short walks, is also recommended. Headaches may be eased by resting in a quiet space, taking paracetamol and trying relaxation techniques.

For more information on managing side effects, Boots Online Doctor advised Britons to consult its dedicated weight loss medicine side effects page.

​How does Mounjaro work?

Mounjaro contains the active ingredient tirzepatide, which works on two different hormonal receptors to achieve weight loss. The drug targets glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptors.

GLP-1 helps regulate blood sugar levels, signalling to the brain to reduce hunger and prevent cravings. It also slows stomach emptying to maintain feelings of fullness for longer periods.

GIP regulates energy balance in the brain and fat cells, enhancing the GLP-1 effect of suppressing appetite and improving sugar control.

By mimicking both of these naturally occurring hormones, Mounjaro has demonstrated greater weight loss potential than medicines that work on GLP-1 alone.

Clinical trials have shown that patients could achieve at least 20 per cent weight loss after using tirzepatide for 72 weeks when combined with healthy lifestyle changes.

The strict eligibility criteria mean only those with the highest clinical need will initially access Mounjaro through their GP. Patients must have a body mass index of more than 40 and at least four obesity-related health conditions.

These conditions include type 2 diabetes, high blood pressure, heart disease, abnormal blood fats, and obstructive sleep apnoea.

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While the mass rollout of Mounjaro on the NHS marks a significant milestone, it has sparked concerns among medical professionals who predict a surge in enquiries for the drug.

Chair of the Royal College of GPs, Professor Kamila Hawthorne, said: "While we recognise the potential benefits of weight-loss drugs, we know many GPs are concerned about the implications of the rollout of weight-loss drugs into general practice, both in terms of workload and training to appropriately initiate and manage these treatments.

"GPs and our teams are already working under intense workload and workforce pressures, and this must be factored into this rollout in order to guarantee it can be delivered safely.

"More widely, while weight-loss medications have a lot of potential benefits for patients who are struggling to lose weight and who meet all the clinical criteria for a prescription, they mustn’t be seen as a 'silver bullet' to aid weight loss.

"We also need to see a focus on prevention, stopping people from becoming overweight in the first place, so they don’t require a medical intervention later."

Weight loss drugs are effective for some slimmers, with the NHS estimating that about 1.5 million people in the UK are already taking them through specialist services or private prescriptions.

However, implementing healthy lifestyle habits such as eating well and getting enough exercise is also key.