Weight loss jabscould cause sudden blindness, the UK regulator has warned after Robbie Williams claimed his vision is "getting worse" due to the jabs.

The Medicines and Healthcare products Regulatory Agency (MHRA) said people taking versions of the jab semaglutide should attend A&Eimmediately if their vision suddenly becomes blurred or clouded over. It has issued guidance warning of a possible rare side effect risk in the form of non-arteritic anterior ischemic optic neuropathy (NAION).

Naion causes a sudden loss of vision in one eye because of reduced blood flow to the front part of the optic nerve. Semaglutide is sold under the brand name Wegovy, prescribed for weight loss, and Ozempic, for Type 2 diabetes.

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The MHRA alert said: “Patients taking semaglutide who notice a change in their eyesight, such as sudden impairment to their vision, or if their eyesight gets worse very quickly in one or both eyes, should urgently attend eye casualty (if available in the area) or A&E.” However the MHRA said studies showed Naion was "very rarely associated" with semaglutide and could only affect up to one in 10,000 people on the jabs.

Singer Robbie Williams, who says he is an early adapter of the weight loss jabs, claimed his vision is blurry and "getting worse", blaming it on the injections. He is convinced Mounjaro injections could be harming his eyesight, recalling a show last year where he sang She's The One to a girl, but struggled to see the fan.

"I want to warn people reading this of the potential risks, to make sure they do their research," he said, "I was quite an early adapter of the jabs but what I’m also noticing is that my eyesight’s not very good. It’s been blurry for a while now, and it’s only getting worse. I don’t believe it’s age; I believe it’s the jabs. I went to an American football game the other night and the players were just blobs on a green field in front of me."

About two million people in the UK are estimated to be taking some form of weight-loss injection, with semaglutide being the market leader. Dr Alison Cave, MHRA’s Chief Safety Officer said: “Patient safety is the MHRA’s top priority and we continually monitor the safety and efficacy of all licensed medicines.

“While the potential risk of NAION for patients prescribed semaglutide is extremely small, it is important that patients and healthcare professionals are alert to the associated symptoms. If you, or someone you care for, is taking semaglutide and you notice sudden loss of vision in one eye, then we advise you to urgently attend eye casualty (if available in your area) or A&E and report it via our Yellow Card scheme.”

Naion is the most common cause of sudden nerve blindness that results in permanent damage. Experts are unsure why weight loss jabs could be causing it. Weekly injections such as Ozempic, Wegovy and Mounjaro slow digestion and reduce appetite by mimicking a hormone called glucagon-like peptide 1 (GLP-1) which regulates hunger and feelings of fullness. They tend to lead to drastic weight loss of up to 20% of body weight and have been linked to a host of health benefits.

They commonly cause side effects such as nausea and stomach cramps and require personalised support from specialists so that weight loss is maintained. Many patients give up the treatment either because they are buying it privately, so can no longer afford it, because they decide the side effects such as vomiting are too much, or because they are not losing weight anymore.

Without drastic lifestyle changes, stopping the jabs usually results in putting all the fat back on. Muscle mass which has also been lost after starting the jabs is typically not regained. Previously semaglutide maker Novo Nordisk has explained how the drugs "are a well-established class of medicines, which have been studied rigorously in clinical trials" and "patient safety is of the utmost importance".

MHRA guidance on potential side effects of semaglutide and on its safe and effective use is available HERE.