Twenty – that’s the number of individual health problems one study has linked to weight-loss jabs.
The complaints identified range from mild fainting episodes to more worrying concerns such as kidney stones and arthritis.
Ziyad Al-Aly, a clinical epidemiologist and chief of research and development at VA St Louis Health Care System in the US, who led the study last year, says he wasn’t surprised by the broad range of effects.
‘GLP-1 receptors are present all around the body – including the brain,’ he wrote in the journal Nature. ‘The drug leads to profound weight loss and, as well as fat, people lose bone and muscle mass – and may become deficient in micronutrients. All of these may explain the broad side-effect profile.’
Here, with the help of experts, we reveal how the drugs might harm the body…
Sight loss
The GLP-1 drug semaglutide (marketed as Ozempic and Wegovy) appears to carry a far higher risk of eye problems than a long list of other drugs including Viagra (sildenafil), which is itself linked to an increased risk of retinal detachment. Analysis of health records from 180 countries, published in the American Journal of Ophthalmology last year, found that people who took semaglutide had significantly higher odds of suffering serious eye conditions such as ischaemic optic neuropathy (damage to the optic nerve which transmits signal from the eye to the brain) and retinal detachment (where the thin, light-sensitive tissue at the back of the eye becomes loose).
Meanwhile, the journal JAMA Ophthalmology reported last year that there was an association between the use of semaglutide and a rare form of blindness due to optic nerve damage, called nonarteritic anterior ischemic optic neuropathy (NAION). Researchers said: ‘There is a low risk of serious ocular side-effects – but a low risk of a big number is a big risk.’
And just last week, the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) issued new guidance about this risk, saying that while it’s very rare, patients taking semaglutide who notice a sudden change in their eyesight should urgently seek medical help.
Exactly why semaglutide can damage eyesight isn’t clear, but research is ongoing.
The GLP-1 drug semaglutide (marketed as Ozempic and Wegovy) appears to carry a far higher risk of eye problems than a long list of other drugs
Furry tongues and bad breath
According to anecdotal reports, some people on weight-loss jabs experience poorer oral health – a dry mouth, bad breath and tooth damage – possibly because the drugs cause an environment that hastens tooth decay.
The repeated vomiting that weight-loss drugs can cause may also damage the teeth, as ‘stomach acid erodes the enamel’, explains Mervyn Druian, a dentist at the London Centre for Cosmetic Dentistry.
‘I always recommend people using these medications stay well hydrated and sip water regularly throughout the day,’ he says.
A lack of important minerals in the diet such as calcium – due to someone eating less overall – may also lead to teeth softening, so it’s important to maintain a healthy, balanced diet.
Anecdotally, people also report changes to their tongue, such as white furry patches, sore spots and numbness. This may be related to how semaglutide reduces saliva production.
‘Reduced saliva means bacteria can thrive and build up on the tongue, causing bad breath, taste changes and a furry appearance,’ says Mervyn Druian.
Thyroid cancer
One of the worries about using GLP-1 drugs is that they may increase the risk of thyroid cancers. Indeed, the drugs carry a warning on the label for this.
However, experts say most of the evidence for the link comes from trials done on mice, and the label warning is there as a precaution.
A 2024 study in the International Journal of Molecular Sciences analysed US patient data and found the incidence of thyroid cancer in semaglutide-treated patients was still less than 1 per cent.
Menstrual problems
GLP-1 medication could lead to menstrual problems in some women, according to a study published a few weeks ago by Union Hospital in Wuhan, China, which looked at adverse effects associated with tirzepatide (Mounjaro).
The researchers analysed US data and found a potential association with tirzepatide and postmenopausal haemorrhage and menstrual disorder, which suggested the jabs were interfering with sex hormones.
But other research suggests GLP-1s improve fertility. Dr Lucy Lord, a consultant obstetrician and gynaecologist at Central Health London, told Good Health that the risks of hormonal side-effects have to be weighed against the significant benefits of taking GLP-1s – particularly for women whose BMI is over 30 or who have conditions such as PCOS (polycystic ovary syndrome) or type 2 diabetes.
‘Most women reporting such side-effects will already be suffering from endocrine and metabolic abnormalities that may adversely impact their fertility,’ she explains.
‘GLP-1 drugs, ethically prescribed, properly monitored and with appropriate timing for conception could considerably increase the chance of a successful pregnancy in these women.’
Tinnitus
GLP-1 medication could make tinnitus worse, according to a 2025 study by Texas A&M University School of Engineering Medicine in the US, which looked at side-effects in people taking GLP-1 drugs for six months.
Researchers found liraglutide (marketed as Saxenda) was linked to an increased risk of developing tinnitus, which is characterised by persistent phantom sounds including ringing and buzzing that have no obvious source. It’s thought to be linked to damaged hair cells in the inner ear or changes in how the brain processes sound.
One possibility is that rapid weight loss affects the Eustachian tube, the narrow passage that connects the middle ear to the back of the throat and helps equalise air pressure. The weight loss may cause changes to the pressure inside the inner ear, leading to tinnitus, according to a review of studies and the US Food and Drug Administration’s (FDA) adverse event database published in Otology & Neurotology last year. Another theory is that these medications might affect micro-circulation in the inner ear, potentially leading to inner ear damage.
Depression
The risk of psychiatric disorders may increase among those taking GLP-1s, according to a major review of previous research, published in Nature in 2024.
Studies involving more than 162,000 people taking GLP-1s revealed a 195 per cent higher risk of depression, a 108 per cent increased risk of anxiety and a 106 per cent increased risk of suicidal behaviour.
The authors wrote: ‘These findings underscore the critical need for physicians to thoroughly assess patient history’ before prescribing the drugs.
However, there’s also good evidence that GLP-1 drugs can reduce symptoms of depression for those with type 2 diabetes (the exact mechanism isn’t clear).
Following a review, the MHRA concluded in 2024 that ‘the available evidence does not establish a causal relationship’ with GLP-1s ‘and suicidal behaviour, suicidal ideation, self-injury and depression’.
And last month the FDA in the US asked drug companies to remove label warnings about a potential risk of suicidal thoughts from GLP-1 weight-loss drugs.
In the UK there is no such warning on the label, but healthcare professionals are encouraged to monitor patients for mood changes, especially if someone has a history of poor mental health.
Gut problems
Nausea is the most common gastrointestinal side-effect linked to GLP-1 drugs, with up to 50 per cent of people affected. Nausea is often worse when starting on the jabs, or when the dose is raised.
Ahmed Ahmed, a consultant bariatric surgeon and president of the British Obesity and Metabolic Specialist Society, says one possibility is that the drugs affect how GLP-1 receptors work on a part of the brain called the postrema, which plays a crucial role in regulating nausea, vomiting and blood pressure.
Diarrhoea is the second most common gastrointestinal side-effect, although it’s typically mild and short term.
The GLP-1 drugs delay gastric emptying, affecting how long food stays in the stomach and intestines.
But in some people this may initially trigger this process to speed up, says Mr Ahmed. ‘Vomiting can also occur due to the impact of the drugs on stomach emptying.’
Constipation is common, too. ‘Food stays in the stomach and gut for longer, leading to harder stools and difficulty passing them,’ says Mr Ahmed.
In rare cases, constipation can lead to complications, such as painful tears in the anus and piles.
‘Ways to reduce this problem include staying hydrated to soften stools and eating a high-fibre diet to bulk out stools and make them easier to pass,’ says Mr Ahmed.
‘Regular physical activity can help stimulate the digestive system and promote regular bowel movements.’
Muscle and bone loss
It’s estimated that a third of weight loss caused by the jabs is loss of muscle and bone. This may be because muscle proteins are broken down faster than they can be built, due to a reduction in nutrient intake.
This decrease in muscle power has a knock-on effect on bone.
Bones need physical stress to encourage new bone formation to replace old bone cells, explains Sammy Margo, a physiotherapist based in London. ‘The reduction in muscle power – and, at the same time, the drop in body weight – means less force is exerted on them,’ she says.
The older you are, the more likely you are to lose muscle and bone while you lose the pounds, as you’re continually losing muscle after the age of 50 anyway, she adds.
The good news is exercise can help prevent this.
‘Activities that put stress on bones, stimulate extra calcium deposits and encourage bone-forming cells into action include resistance training, such as squats or using resistance bands, and weight-bearing exercise such as brisk walking. These are essential if you’re using the medications.’
Sammy Margo, a physiotherapist based in London, says doing activities that put stress on bones are essential if you’re taking GLP-1 drugs
Pancreatitis and gallstones
The MHRA recently urged doctors to ‘be alert to initial symptoms such as severe, persistent stomach pain that may radiate to the back and may be accompanied by nausea and vomiting’ in patients taking GLP-1 agonists. That’s because of the ‘small risk of severe acute pancreatitis’.
It’s thought that this occurs due to the drugs encouraging the over-production of digestive juices in the pancreas, as there are GLP-1 receptors on exocrine duct cells that make digestive juices. These juices can build up, leading to inflammation.
‘Pancreatic inflammation is dangerous because the inflammatory process can cause complications such as cell death in the pancreas itself, potentially leading to sepsis and even death,’ says Dr Christian Macutkiewicz, a consultant general and hepato-pancreatico-biliary surgeon at Manchester Royal Infirmary.
‘However, most cases are mild and self-limiting,’ he says, adding that there is no evidence that one GLP-1 drug is worse than the other.
‘Rarely, people who use weight-loss jabs can develop gallstones (formed of hardened bile). While these don’t usually cause symptoms, they can block the pancreatic duct, which can lead to inflammation of the pancreas,’ he adds. Some experts are blaming a recent rise in gallbladder removal on GLP-1 drugs causing gallstones.
Weak pelvic floor
Losing weight quickly can affect any muscle – even those that support the pelvic floor, says Dr Sherry Ross, an associate professor of urology at the University of North Carolina at Chapel Hill in the US. This raises the risk of a prolapse, as well as urinary or faecal incontinence.
‘Having any, or all, of these uncomfortable and embarrassing symptoms can have a negative effect on sexual desire,’ says Dr Ross. However, weight loss may ultimately boost desire, she adds.
Physiotherapist Sammy Margo’s advice is for ‘women to proactively strengthen their pelvic floor during rapid weight loss periods’ with pelvic floor exercises.
Ozempic vagina, a popular hashtag on social media, refers to sagging of the labia or vagina caused by fast weight loss but is ‘not a medical diagnosis’, says Dr Ross. ‘But some people use it to refer to vulvovaginal changes while on a GLP-1 agonist,’ she adds. ‘Rapid weight loss on any body part can affect the skin over the fatty tissue lost – including the lower belly, pubic mons, and inner and outer labia.’
It can affect all ages, although older women whose skin has already lost elasticity are more prone to it, she says.
Wrinkles
Any rapid weight loss can have an ageing effect on the face because it results in a loss of fat deposits, ‘leading to sunken cheeks, eyes, and temples, and making the bones of the face appear more prominent’, says Omar Quaba, a consultant plastic surgeon based in Edinburgh.
As the skin sags, existing wrinkles may be accentuated. The folds around the nose can become more prominent, too, while the skin around the jawline becomes looser.
The term ‘Ozempic face’ was coined in 2023 by a plastic surgeon in the US who was seeing the impact of weight-loss jabs among his patients.
The effect is more pronounced in people with naturally leaner faces, or older adults with lower collagen levels, says Mr Quaba.
Menopausal and post-menopausal women are particularly vulnerable as almost a third of skin collagen is lost during the first five years after menopause.
Fat loss in the face can be permanent, adds Dr Justine Hextall, a consultant dermatologist at the Tarrant Street Clinic in Sussex.
To minimise skin sagging, ensure weight loss is steady, at around 0.5kg per week, suggests Dr Hextall.
‘Ensure that a healthy, balanced diet is in place, too, with adequate nutrients, including protein.’
Hair loss
The evidence about GLP-1 drugs and hair loss is mixed, according to a review of available research published last September in the journal Cureus – but the researchers said the greater the weight loss, the more severe any hair loss experienced might be.
They pointed to a trial involving Wegovy where 5 per cent of people who lost more than 20 per cent of their body weight experienced hair loss, compared to 2.5 per cent of those who lost 20 per cent or less.
There are thought to be multiple mechanisms. One major potential cause is the stress of rapid weight loss on the body, which can lead to temporary shedding of hair, a condition known as telogen effluvium.
‘Any major change causing physical, emotional, nutritional and hormonal stress on the body can have this effect, ‘ says Stephen Carson, a trichologist based in London.
‘However, this is not permanent, and once the stressor has been removed [i.e. stopping GLP-1s], normal hair growth will resume.’
Another form of hair loss he’s seen in some people taking the jabs is alopecia areata, where the immune system attacks hair follicles, causing bald patches. ‘But again, I suspect that this was caused by the sudden shock of the weight loss,’ he says.
‘Alopecia areata can resolve fully, but it depends on the individual. To look after your hair while on these jabs, lose weight gradually, and make sure you consume lots of protein, vegetables, oily fish or flax seed oil, legumes and nuts, which all contribute to a healthy scalp. And make sure you’re well-hydrated.
‘I did lose weight – but the jabs left me suicidal’
Sara Peterson*, 34, a single stay-at-home mother of three, lives in Bradford with her daughter, 14, and son, six. She says:
Last year should have made me the happiest I’ve ever been. I’d struggled with my weight for most of my adult life, reaching 17st 6lb [at 5ft 3in, this made her BMI over 40] and a size 24, which made looking after my children – and even walking – difficult.
Then in June I started on semaglutide – and for the first five months, I loved it. I was prescribed the jabs by a company I found online that works with the NHS. It sent my request to my GP who signed it off, and that was it (the same GP had previously rejected my request for the jabs as I didn’t have adequate health complaints to get it on the NHS).
I had a little sickness if I ate something too sweet, but the weight just fell off – I’d lost over 3st by October and was buzzing.
I was now a size 14 and could fit into ‘normal’ clothes for the first time in years. I could run and play with my son again. I felt great.
Then suddenly – not quite overnight, but very quickly – I became depressed. Nothing had changed in my life apart from the weight loss and the jabs.
My depression got darker and darker to the point where I started planning to take my own life and thinking about where I would send the children.
The previous year I’d been prescribed the very smallest dose of a mood-stabilising drug, quetiapine, because I’d been feeling down – but that wasn’t anywhere near how I felt in October.
I’m quite an upbeat person, the girl who makes everyone laugh – but my friends were saying it was like my personality had disappeared. I didn’t want to go out or socialise, even though I was the slimmest I’d been in years.
I was still on my mood-stabilising drug and asked the doctor what I could do – they didn’t even give me an appointment, just doubled my dose. But it made no difference.
In the back of my mind I kept telling myself that this wasn’t me – but other times, I’d be thinking of more ways to end my life and that really terrified me.
It was only when I joined a few Facebook groups for people on weight-loss jabs, where others were talking about depression and suicidal thoughts, that I realised the jabs might actually be making me feel this way.
I came off the drug earlier this month – by which time my weekly dose (which had started at 0.5mg) was 1.7mg – and almost immediately the depression, and the thoughts of killing myself, disappeared.
I’m now just over 12st and I really don’t want to put weight back on, though with the depression lifting, I’m more motivated to keep the weight off.
But I’d prefer to be overweight and happy – and here for my children – than slim and dead. It’s not worth the risk.
I’m warning so many people – like mums at the school gate – that these jabs can affect your mood. They’re really not worth it.
INTERVIEW BY JILL FOSTER
* Name has been changed
For help and confidential support, call the Samaritans on 116 123 or go to samaritans.org
‘I’d never had problems with my vision until I started on GLP-1s’
James Holland is now on bifocals for reading and long-distance sight, after he started using GLP-1 jabs
James Holland, 50, director of a personal training company, lives in Mansfield with wife Rachael, 47, a deputy headteacher, and their two children, aged seven and ten. He says:
After returning from holiday last summer, I noticed I’d put on weight and though I wasn’t obese, at 6ft and 15st 1lb (BMI 29, making me ‘overweight’), I could do with losing a stone or so.
I ordered three 5mg pens online, for around £100 each – and it was worryingly easy. There were no medical checks or discussion of serious side-effects. But I vowed to only use the three pens, as an experiment.
Within ten days I had nausea; very bad, smelly burps; flatulence; and terrible diarrhoea – at one point I was at a football match and jumped up when my team scored a goal, and I lost control of my bowels and had to leave my underwear in a bin at the ground. It was horrible.
But I was losing weight, so I persevered. After week six my stomach symptoms and sickness eased off – but I noticed a change in my eyesight.
Peering at my phone early one morning, I realised that the words in a text were blurry, until I brought the device closer to my face.
I thought it was my age, perhaps – or the fact I do a lot of computer work – so I went to an optician and they gave me prescription glasses. I didn’t think much about it.
But in the months that followed, I found my long-distance vision was going, too: I used to be able to read licence plates easily, but now I was squinting. I was like an old man, looking over his glasses to read things.
I went back to the optician, and now I’m on bifocals for reading and long-distance vision.
At the time, I didn’t put two and two together, but when – three months after starting – I’d used my GLP-1 pens up I did some more research about my deteriorating eyesight and saw that eyesight could be affected by the medication.
And now it’s permanent, so I’ll be wearing glasses for life. If I’d known the drug would affect my eyesight there is no way I would have taken it.
I’ve been warning anyone who will listen about the fact that this is a possible side-effect of taking the jabs.
Another worrying effect has been the high amount of muscle deterioration I noticed. I use special scales to monitor my body composition and while I lost more than 3st – going as low as 11st 11lb – 75 per cent of it was muscle mass, not fat. And people would comment that I looked ill.
I’ve put on about half a stone now – and that’s pure muscle.
