WEIGHT loss jabs have been linked to an eye condition that can cause blindness.
Researchers found diabetes patients prescribed semaglutide, the active ingredient in Ozempic and Wegovy, were more than four times more likely to be diagnosed with non-arteritic anterior ischemic optic neuropathy (NAION).
Meanwhile, those who were overweight or obese prescribed the drugs were more than seven times as likely to develop the condition as those on other weight loss medicines.
NAION, which is uncommon, occurs from a lack of sufficient blood flow to the optic nerve.
People typically suffer sudden vision loss in one eye, without any pain, and patients often notice the issue on waking up.
There are no current treatments for NAION and vision often does not improve.
Joseph Rizzo, a professor of ophthalmology at Harvard Medical School in the US, who led the new study, said: “The use of these drugs has exploded throughout industrialised countries and they have provided very significant benefits in many ways.
“But future discussions between a patient and their physician should include NAION as a potential risk.
“It is important to appreciate, however, that the increased risk relates to a disorder that is relatively uncommon.”
NAION is thought to affect 10 out of 100,000 people in the general population.
Prof Rizzo said the visual loss caused by NAION was painless and could progress over many days before stabilising.
He and colleagues decided to investigate a potential link between semaglutide and NAION last summer after three patients in his practice were diagnosed with vision loss caused by NAION in one week.
All three patients were taking semaglutide, which mimics a fullness hormone in the gut and reduces appetite.
To investigate possible links, researchers examined data from more than 16,000 patients from Mass Eye and Ear, a Harvard teaching hospital, treated over a six-year period.
They compared patients who had received prescriptions for semaglutide with those taking other diabetes or weight loss drugs.
Among 16,827 patients, 710 had type 2 diabetes, with 194 prescribed semaglutide.
Some 979 patients were overweight or obese, with 361 prescribed semaglutide.
This is information we did not have before and it should be included in discussions between patients and their doctors
Professor Joseph Rizzo
In people with type 2 diabetes, 17 NAION events occurred in patients prescribed semaglutide compared to six on other diabetes drugs.
Over three years, 8.9 per cent people on semaglutide had NAION compared to 1.8 per cent on the other drugs, the researchers found.
Meanwhile, in patients who were overweight or obese, 20 NAION events occurred in people prescribed semaglutide, compared to three on other drugs.
Over three years, 6.7 per cent people on semaglutide had NAION compared to 0.8 per cent on other drugs.
The researchers said further, larger studies were needed, adding that Mass Eye and Ear saw an unusually high number of people with rare eye diseases.
They added that the number of NAION cases seen over the six-year study period was relatively small.
Prof Rizzo said: “Our findings should be viewed as being significant but tentative, as future studies are needed to examine these questions in a much larger and more diverse population.
“This is information we did not have before and it should be included in discussions between patients and their doctors, especially if patients have other known optic nerve problems like glaucoma or if there is pre-existing significant visual loss from other causes.”
Graham McGeown, honorary professor of physiology at Queen’s University Belfast, said the authors had acknowledged there were limitations to the study, published in JAMA Ophthalmology.
But he said: “This research does suggest an association between semaglutide treatment and one form of sight-threatening optic neuropathy, but this would ideally be tested in larger studies.
“Given the rapid increase in semaglutide use and its possible licensing for a range of problems other than obesity and type 2 diabetes, this issue deserves further study, but possible drug side effects always need to be balanced against likely benefits.”
Novo Nordisk, which makes Wegovy and Ozempic, has been contacted for comment.
Weight loss jabs are a hot media topic at the moment, with hundreds of success stories from people who shed the pounds.
In March 2023, the NHS announced it would make Wegovy, a drug made by Danish firm Novo Nordisk, available on prescription to thousands of obese Brits.
It contains the drug semaglutide, which is said to have helped reality star Kim Kardashian and Twitter boss Elon Musk lose weight.
Wegovy, which helped a third of people reduce their weight by 20 per cent in trials, is now available from pharmacies like Boots.
How do they work?
The jabs work by suppressing your appetite, making you eat less and therefore lose weight.
To do this, semaglutide mimics the role of a natural hormone, called GLP-1.
GLP-1 is part of the signalling pathway that tells your body you have eaten, and prepares it to use the energy that comes from your food.
London GP and founder of wellgoodwellbeing.com, Dr Zoe Watson, said: “Your body naturally produces an appetite regulating hormone called glucagon-like peptide-1.
“These jabs work by regulating your appetite, which can lead to eating fewer calories and losing weight.”
Aren’t they diabetes drugs?
Semaglutide, the active drug in Wegovy, was originally sold under the name Ozempic specifically for diabetes patients.
But people started noticing it helped suppress their appetites, stopping them eating as much and helping them shed the pounds.
Novo Nordisk then developed Wegovy, which contains the same chemical but at higher doses specifically to aid weight loss.
Wegovy is not prescribed for diabetes patients.
Can I get them?
Wegovy is offered on prescription to obese adults given specialist weight loss treatment.
The NHS currently also offers a similar drug called Saxenda, or liraglutide.
Both are only available on Tier 3 and Tier 4 weight management services, which means you have to be referred to weight management clinics led by experts.
GPs can’t prescribe them on their own either, Dr Watson said.
The jabs have to be taken as part of an overall programme to help with lifestyle changes and psychological support to get the best effect from the medication prescribed.
Despite being approved for use, supply of Wegovy on the NHS has been postponed indefinitely because of a surge in worldwide demand.
Supply was also halved in the US because of the skyrocketing demand.
Are there any risks?
Like all medicines, the jabs do not come without side effects.
Around half of people taking the drug experience gut issues, including sickness, bloating, acid reflux, constipation and diarrhoea.
Dr Sarah Jarvis, GP and clinical consultant at patient.info, said: “One of the more uncommon side effects is severe acute pancreatitis, which is extremely painful and happens to one in 500 people.”
Other uncommon side effects include altered taste, kidney problems, allergic reactions, thyroid tumours, gallbladder problems and hypoglycemia.
What other options are there?
Mounjaro (brand name for tirzepatide) also came onto the market in early 2024.
Like Wegovy, tirzepatide stems from a drug originally designed to treat diabetes.
The weekly injection helped overweight people drop more than two stone in 18 months.
It is available with to order with a prescription online from pharmacies including Superdrug and LloydsPharmacy Online Doctor.
It works in a similar way to Wegovy and Saxenda, but is more effective.
Dr Mitra Dutt from LloydsPharmacy says: “Based on clinical trials, 96 per cent of people were able to lose more than five per cent of their body fat using Mounjaro. In similar trials, 84 per cent of people lost more than five per cent of their body weight on Wegovy, and 60 per cent on Saxenda.
“Mounjaro works by activating two hormonal receptors (GIP and GLP-1), which enhance insulin production, improve insulin sensitivity, and work to decrease food intake.”
The popularity of ‘skinny jabs’ is booming after trials showed they cause rapid weight loss and may bring a raft of other health benefits.
With Wegovy, you can expect to see 15 per cent weight loss on average. That is a 31lb for a person weighing 15st, taking them to 12st 11lb.
Mounjaro is more effective, reducing weight by 20 per cent, and Saxenda is the least effective, with five per cent weight loss, on average.
Some jabs are available on the NHS, but eligibility hinges on body mass index and weight-related health issues like hypertension.
Private demand, including from celebs like Jeremy Clarkson and Boris Johnson, is said to have squeezed NHS supplies.
The jabs can be bought online for about £150 per month or even from unlicensed beauticians.
But while they may help people shed some pounds, they come with a host of potential side effects.
Ian Budd, pharmacist at Chemist4U and MyBMI, said: “This commonly may include nausea, diarrhoea, constipation, headache and dizziness.
“The frequency and severity of side effects can vary, and some people may experience none at all.
“Long-term effects of injectable weight loss medications are still being studied, and the safety profile of these medications over extended periods is not yet fully understood.”
Other side effects reported include vomiting, abdominal pain, fatigue, flatulence and acid reflux.
Elsewhere, research has shown that semaglutide could reduce the risk of heart failure, heart attack, stroke, addiction, Parkinson’s and even Alzheimer’s.
