Why Mounjaro users’ hair is falling out

Weight loss jabs aren’t just causing people to shed the pounds — many users say their hair is falling out, too.

Since Mounjaro was approved for obesity treatment in February 2024, more than 1.5 million people in the UK have been prescribed the drug through private clinics and the NHS.

But 16 months on, users are reporting a raft of unexpected side-effects.

Many have taken to social media to complain of decreased libido, a reduced interest in alcohol — and, most upsettingly for some, dramatic hair loss.

A scroll through the Mounjaro forum on Reddit reveals thousands of posts from devastated users struggling with thinning, lacklustre locks. Some have even shared photos of their fingers and hairbrushes wrapped in coils of fallen strands.

‘I’m eight months in and within the last couple of weeks, the hair loss has been scary. Anybody experiencing this, does it eventually slow down?’ wrote one forum member.

‘I’m not sure if it’s length of time on the medication or if it’s the 10mg dose, but I can’t spare much more.’

However, leading experts say the problem may not lie with the drug itself but with how people are using it.

Dr Ed Robinson, who runs an aesthetics clinic in Manchester, says he’s seeing a growing number of clients worried about thinning hair — and often, he tells them the real issue is nutrient deficiency.

He told the Daily Mail: ‘It’s a very common side effect that happens as a result of using these GLP-1 medications, but it’s not the drug itself that causes you to lose hair.’

‘It’s a combination of two things. First of all, the people who use these medications obviously eat significantly less because it suppresses their appetite.’

‘A lot of people use either more than the recommended dose or calorie restrict even more than is recommended, and that can result in really quite rapid weight loss.’

‘And that can effectively cause quite quite quick nutritional deficiencies.’

GLP-1 weight loss drugs reduce appetite by silencing ‘food noise’—the constant mental urge to snack or overeat—which means many users end up picking at meals or grabbing nutritionally poor snacks on the go.

A sharply reduced calorie intake means the body may not get the nutrients it needs to function properly—or, in extreme cases, even meet basic requirements—because the limited food consumed often lacks essential fats, vitamins and minerals.

Dr Robinson added that the idea you can replace a balanced diet with a handful of supplements is a myth: ‘The common belief that a fistful of supplements every morning is just as good as a balanced diet is very wrong.’

‘Vitamins D, A, K and E are all fat soluble vitamins, and this means that they simply will not absorb if you’re taking them without fat in your diet. 

‘When it comes to Vitamin D especially, a lot of people take them first thing in the morning on an empty stomach—not eating any fat—so they’re actually not absorbing any of it at all. 

‘For people who are taking vitamins while calorie restricting, and in the case of people taking weight loss jabs who are probably eating less anyway, they’ll get minimal absorption from multiple different vitamins.’ 

‘Protein is really important, and that actually ties into one of the other things that you often see with GLP-1 analogues, which is muscle wasting.’

But it’s not just the major organs which need calories to keep working—they are literally required by the whole body from head to toe. 

‘Nutrients and fats are also important in terms of maintaining the strength and formation of hairs,’ said Dr Robinson. 

‘Protein is the main element you need, but even things like iron, biotin, vitamin D and magnesium are all very important in terms of growing your hair as well. 

‘By restricting your calories and your food intake quite a lot, you can end up deficient in these nutrients and minerals quite quickly, and that can result in your hair becoming thinner and more brittle.’ 

Worryingly, he adds that it can also stimulate a hair loss condition called telogen effluvium which is when the body sheds a substantial amount of hair due to stress, shock—or in mot jabbers’ cases, malnutrition. 

Dr Robinson said: ‘The hair growth cycle has two phases; first is antigen, which is a growing phase, and then there’s a resting phase called telogen. 

‘During the antigen phase, your hairs grow, and then at some point they shift and they detach from the follicle, and sit in your scalp waiting to fall out.

‘In many people, that phase can last several months, a lot of the time you technically have less hair than you realise, but it’s just sitting there waiting to fall out.’ 

Without adequate nutrients to grow new hairs, it means that when the hairs shed, there is nothing to replace them with, causing baldness and thinning patches.  

‘There are certain things that can make that hair falling out phase happen much quicker, and one of them is calorie restriction. It encourages those cells to go into telogen, and then they just shed.

‘The problem is that if you’re if you’re calorie restricting, and then you get all your telogen hairs to fall out, then you don’t have new hairs to grow, causing quite rapid thinning and loss.’ 

And in a blow to women going through perimenopause and menopause—who are a main demographic of weight loss jab users—hair loss can be even more extreme as changes in hormone levels play havoc with women’s scalps.

 Dr Robinson concluded that it’s vital that anyone using weight loss medication does it under strict medical supervision, to reduce side effects—and to take their nutrition seriously. 

He said: ‘When you’re when you’re on these treatments, you should be being assessed in terms of what your diet is, and your diet should still be well balanced, even if your calories are restricted. 

‘If you are experiencing these problems, then you should raise it with your doctor, because you may well either need your dose adjusted, or there are other preventative treatments that you can use. 

‘For hair loss, medications like Minoxidil can help, as can non-surgical treatments. 

‘But I would always advise having your dose adjusted if you’re losing weight too quickly, rather than having more treatments to cope with the side effects.’ 

GPs can now prescribe the drug to patients with a BMI over 40 – classed as severely obese – and at least four obesity-related health conditions, such as type 2 diabetes, high blood pressure or sleep apnoea.

Mounjaro is a weekly jab that can help patients shed up to a fifth of their body weight in a year.

More than a million people in the UK are already using it via private clinics, where it costs around £250 a month.

However, until now, only a limited number of patients could access it on the NHS via specialist weight-management services.