Weight loss jabs relied on by millions of slimmers raises the risk of a debilitating eye condition that could lead to permanent vision loss, according to new research.
Semaglutide — the powerful ingredient behind Wegovy and Ozempic — has long been hailed a monumental breakthrough in the war on obesity.
But American doctors, who tracked over 37 million people, said the injections put users at higher risk of nonarteritic ischemic anterior optic neuropathy (NAION).
The condition, known as an ‘eye stroke’, occurs when the vessels supplying blood to the optic nerves become blocked.
The loss of blood supply deprives the optic nerve of oxygen and results in damage to all or part of the nerve.
However, overall risk of developing the condition while on the jabs remained ‘low’, experts said.
The medics cautioned further research was still vital to further prove the link and said they couldn’t be sure why the medicines, collectively known as GLP-1 agonists, may trigger the condition.
It comes as separate research released last month detailed nine cases of US patients who went blind after taking semaglutide or tirzepatide, the active ingredient behind Mounjaro.
American doctors, who tracked over 37 million people, said the injections put users at higher risk of nonarteritic ischemic anterior optic neuropathy (NAION)
The condition, known as an ‘eye stroke’, occurs when the vessels supplying blood to the optic nerves become blocked
At the time, they said while the exact cause was unclear, the rapid drop in blood sugar caused by the drug could damage blood vessels in the eyes.
This is because the sudden change in pressure can cause fluid to leak out of delicate blood vessels in the retina, leading to swelling and retina damage.
Around half a million people in the UK and some 2million in the US are now thought to be using the jabs, which can help them lose up to 20 per cent of their bodyweight in just a few months.
In the study, the researchers from Johns Hopkins University in Baltimore, Maryland, found of the 37 million adults, there were 166,932 patients on type 2 diabetes drugs, including semaglutide.
Writing in the journal JAMA Ophthalmology, the researchers said: ‘We observed an increased NAION risk with semaglutide exposure relative to non-exposure.’
They also observed an ‘increased risk’ among those on semaglutide compared to ‘users of non–GLP-1 drugs empagliflozin and sitagliptin,’ they added.
They added: ‘In the absence of a known mechanism for this association, we urge clinicians to weigh the concern for an increased risk of a rare but potentially blinding eye condition with the many therapeutic benefits of semaglutide.’
There are currently no treatments for NAION or an ‘eye stroke’, which affects around one in 10,000 people, and vision often does not improve.
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Unlike other strokes caused by a loss of blood supply, there is no weakness, numbness or loss of speech.
People typically suffer sudden vision loss in one eye, without any pain, and patients often notice the issue on waking up.
It comes as a separate study published in the same medical journal last month suggested that the drugs may trigger debilitating vision issues including NAION.
They noted this was likely due to the fact the jabs rapidly lower blood sugar levels which could damage blood vessels in the eyes — not that the injections themselves were ‘toxic’.
The report detailed the cases of nine adults, aged 57 on average, who took either semaglutide or tirzepatide.
Seven were later diagnosed with NAION. But most noticed their vision improving within days or weeks of stopping the drugs.
According to the report, one woman in her 50s developed NAION the day after her first semaglutide injection.
She woke up the morning after the injection with ‘painful vision loss’ in her left eye.
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Tests revealed swelling in her optic nerve and damaged blood vessels in her retina.
The woman stopped taking semaglutide and her insulin, with follow-up appointments confirming her vision returned to normal two months later.
However, two weeks after restarting semaglutide to control her diabetes, the vision loss returned.
She was diagnosed with severe optic nerve swelling, and her vision returned to normal seven months later. It was unclear if she stopped semaglutide a second time.
Health officials in Denmark, where Ozempic manufacturer Novo Nordisk is based, are also currently investigating the links between semaglutide and vision loss.
Like any medication, the jabs are known to cause side effects that vary in both frequency and severity.
Other reported problems include constipation, fatigue, stomach pain, headaches and dizziness.
Bizarre symptoms, such as hair loss, have also been reported among some patients.
Doctors have also long told how they are treating increasing numbers of slim women who end up in hospital after falsely telling online chemists they are overweight to pass eligibility checks.
Under official guidelines, only patients who have a body mass index (BMI) of over 35 and at least one weight-related health problem like high blood pressure, or those who have a BMI of 30 to 34.9 and meet the criteria for referral to a specialist weight management service, should be prescribed Wegovy.
In the UK, law forbids the sale of such drugs without a prescription from a medical professional.
In December, advertising officials issued a warning to advertisers, businesses and influencers to remove online and social media ads for weight-loss prescription-only medicines targeted at members of the public.
This followed a MailOnline investigation that found social media influencers were being encouraged to illegally promote prescription weight-loss jabs to their thousands of followers.
