Teenagers, predominantly boys, are reportedly taking the cancer drug erdafitinib in the belief it can help them grow taller, a trend linked to the wider 'looksmaxxing' craze. The medication, often called 'erda', is a common topic in online biohacking and self-improvement groups, where one user described it as a 'height saviour'.
A 16-year-old Redditor explained their decision to try the drug, writing: 'My main motivation for height growth is being seen as less of a man, I hate walking around knowing other people are better than me. I know this will give me the best chance of at least one more inch.' On TikTok, some posts claim '6'2" is the new 5'11"' as a reason to 'blast erda ASAP', while others urge followers to message for sourcing and dosage tips to 'heightmaxx before it's too late'.
Real-world side effects reported by users
However, users who spoke to Rolling Stone describe a more complicated reality. Zak, a 17-year-old TikToker from New York, said that during two years of intermittent use he experienced joint pain, nosebleeds and severe dry skin. Another 17-year-old alleged his fingernails fell off within two months of taking erda, though he also used other growth supplements.
Erdafitinib, sold under the brand name Balversa, is a tyrosine kinase inhibitor (TKI) licensed in the UK for certain types of bladder and urinary tract cancer. It works by blocking the activity of the growth-driving TKI protein in certain cells, including tumours. While some studies suggest it may speed up bone growth in children and teenagers, evidence is limited.
Manufacturer and regulator warnings
A spokesperson for manufacturer Johnson & Johnson said: 'It has not been approved to increase height, and its safety and effectiveness have not been established for that purpose or for any use in any children or adolescents.' Despite this, erdafitinib is still available to buy online without a prescription, with sites showing only a disclaimer that it is 'for research use only'.
A spokesperson for the Medicines and Healthcare products Regulatory Agency (MHRA) told Metro: 'Erdafitinib is approved in the UK for a specific group of adults with advanced urothelial cancer and should only be prescribed by a healthcare professional experienced in the use of anticancer therapies. Labelling a product "for research purposes" does not automatically place it outside medicines regulation. Where there is evidence that such a claim is being used to circumvent medicines regulations, the MHRA can take appropriate regulatory action.'
Health experts advise against off-label use
Dr Donald Grant, GP and senior clinical advisor at The Independent Pharmacy, warned against off-label use. 'My advice is simple: don't take it,' he told Metro. 'The side effects can be significant, ranging from eye problems that can permanently damage your vision, to painful mouth ulcers, diarrhoea, dry and peeling skin, nails loosening or falling off, and hair loss. Some children treated with it for cancer have had bone and joint problems too. There's no proof it makes healthy teenagers taller, and once the growth plates in your bones close towards the end of puberty, no medicine can add height.'
Common side effects listed on the Balversa website include nails separating from the bed or poor nail formation, mouth sores, diarrhoea, increased creatinine and alkaline phosphatase levels, changes in liver function, anaemia, low sodium, tiredness, dry mouth, dry skin, decreased phosphate, decreased appetite, taste changes, constipation, high calcium, dry eye, hand-foot syndrome, high potassium, hair loss, and fluid buildup behind the retina.
Dr Grant also noted that heightmaxxing 'puts enormous pressure on young men to look a certain way,' when 'height is largely decided by genetics, and there's no shortcut.' He added: 'What worries me most is that this trend has moved from harmless tips into young people buying cancer drugs online and experimenting on themselves.'
Advice for parents
Omar El-Gohary, superintendent pharmacist at IQ Doctor, advises parents to start with an open conversation rather than confrontation. 'If they're thinking about buying it, ask them to show you what they've seen online and what they hope it'll do,' he told Metro. 'If you find an order confirmation or a packet, start with, "Have you taken any? I need to know so I can help." If they've bought it but haven't taken it, keep it out of reach.'
If a child has swallowed erdafitinib, El-Gohary says to call 999 or go to A&E immediately, without waiting for symptoms. Parents should keep packaging or order details and tell medical staff what was taken, how much and when. Warning signs include hip, groin, thigh or knee pain, limping, and vision changes, all warranting urgent medical assessment.
El-Gohary also stressed understanding the reasons behind a teenager's interest. 'What worries me is how quickly a teenager can go from wondering why their friends have had a growth spurt to feeling they need to take a cancer drug before they miss their chance,' he said. 'Puberty starts at different times, so two teenagers in the same class can be at very different stages of growth. I'd ask what's made height feel so important lately. Has someone been teasing them? Have they seen a video that made them feel they're running out of time? That gives you something specific to help with.' He added that a GP can check height measurements over time if there are concerns about growth.
