MHRA safety advice for weight loss medicines

The MHRA is the UK medicines safety regulator. This page sets out its published advice for people taking GLP-1 medicines.

Common side effects

Nausea, vomiting and diarrhoea are common. They can occasionally cause severe dehydration which needs hospital care. Source: MHRA.

Pancreatitis

Acute pancreatitis is a known side effect. The MHRA describes the overall frequency as uncommon, with rare severe and fatal cases. On 29 January 2026 the MHRA strengthened the warnings for all GLP-1 medicines. Source: MHRA.

• The sign to act on: severe stomach pain which does not go away. The pain may spread to your back and may come with nausea or vomiting. Get urgent medical help.
• The numbers: from 2007 to October 2025 the Yellow Card scheme received 1,296 UK reports of pancreatitis linked to these medicines, 19 of them fatal. About 25.4 million packs were dispensed over five years.
• After a confirmed case: the MHRA says the medicine should not be restarted.

Eyes

Semaglutide has been linked in rare cases to an eye condition called NAION. Sudden loss of vision, or vision which worsens fast, needs urgent medical attention. Source: MHRA.

Mood

An MHRA review found no causal link between these medicines and depression, suicidal thoughts or suicide. Monitoring continues. Source: MHRA.

Contraception

Mounjaro may reduce the effectiveness of oral contraceptives in people with overweight or obesity. The MHRA advises adding a barrier method, such as condoms, for four weeks after starting and for four weeks after any dose increase. A non-oral method, such as the coil or implant, is another option. Source: MHRA.

Pregnancy and breastfeeding

The MHRA says not to take these medicines during pregnancy, while trying for a baby or while breastfeeding. Stop before trying to conceive:

If you think you are pregnant, contact a healthcare professional straight away. Source: MHRA.

Surgery and anaesthetic

These medicines slow the emptying of the stomach. Tell your healthcare team, including the anaesthetist, before any procedure. Keep taking your medicine as normal unless your doctor tells you otherwise. Source: MHRA.

Using a pen

After the four recommended doses, dispose of the used pen. Do not try to draw out any medicine left inside. Source: MHRA.

Report a side effect

Report any suspected side effect, or a suspected fake, through the Yellow Card scheme. For an urgent health problem call 999 or go to A&E. For advice call NHS 111.

Foundayo

For Foundayo the MHRA lists nausea, constipation, diarrhoea, vomiting, indigestion and abdominal pain, and says the safety and effectiveness will stay under close review. Source: MHRA.

Questions

Official sources

Every rule on this page comes from the sources below. GLP Index checked each one on 8 October 2026.

1. Medicines and Healthcare products Regulatory Agency. GLP-1 medicines for weight loss and diabetes: what you need to know. First published 5 June 2025, updated 5 February 2026.
2. Medicines and Healthcare products Regulatory Agency. Drug Safety Update: strengthened warnings on acute pancreatitis. 29 January 2026.
3. Medicines and Healthcare products Regulatory Agency. Yellow Card scheme: report a side effect or a fake medicine. Live service.
4. Medicines and Healthcare products Regulatory Agency. UK first in Europe to authorise orforglipron for weight management and type 2 diabetes. 10 August 2026.

More on UK rules

• GLP-1 medicines in the UK: which are licensed for weight loss
• Who can get weight loss medicine in the UK
• Weight loss injections on the NHS: who qualifies and when
• Buying weight loss medicine online: the UK rules
• Why weight loss medicines are not advertised in the UK
• Who regulates weight loss medicines in the UK
• UK weight loss medicine timeline: every key decision
• NHS vs private: what weight loss medicine costs in the UK
• All UK rules pages

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