Illegal melatonin dietary supplements with 5x beginning dose present in marketplaces, Which? warns
The medication is only available with a prescription in the UK, but has been found on online marketplaces
Melatonin is a hormone that plays a role in regulating sleep(Image: GETTY)
Melatonin is a hormone that plays a critical role in regulating your sleep and, while it is available in the UK, you need a prescription to purchase it. However, illegal melatonin supplements have been found on multiple online marketplaces, potentially risking the health of buyers.
Which? research discovered some of the illegal products didn’t even mention melatonin in the name, while others had ‘excessively high’ recommended doses. Many were found to have 10mg, which is five times the usual starting dose doctors prescribe and equivalent to the maximum dose the NHS recommends for people with long-term insomnia.
One product the consumer watchdog found advertised on Temu claimed to contain 30mg of melatonin. Some sellers tried to hide the fact that the products contained melatonin in order to stop platforms from detecting the illegal products and removing them.
Which? found melatonin being illegally marketed on marketplaces including AliExpress, Amazon, eBay, Superdrug and others between October 2025 and January 2026. The hormone was even available in a range of products from supplements to patches and tea.
Sue Davies, Which? head of consumer policy, said: “If shoppers buy from sellers illegally advertising melatonin, there is no telling what the products will contain – they could contain too much melatonin or other potentially harmful substances, which could lead to dangerous side effects.”
Melatonin naturally occurs in your body. For most people, melatonin levels rise at night and return to normal during the day, controlling when they sleep.
People with sleep disorders or trouble sleeping may rely on a synthetic version of melatonin to top up their body’s natural supply at the right time of day to help them fall asleep quickly and rest for longer. However, the product must be taken with proper medical supervision as it can interfere with other common medications like contraception and can trigger side effects like headaches and mood changes.
Which? is calling for better oversight of the supplement industry to ensure unsafe and illegal products are taken off the market. Particularly because the sellers are operating outside of legal channels, meaning that the products could contain too much melatonin or none at all, which could have unpleasant side effects.
Which? noted that some products initially discovered have since been removed, but added that it should never have been listed for sale in the first place. The experts warned that vulnerable groups, like children, may be especially at risk, as they should not be given melatonin without medical supervision. Some of the marketplaces involved in the investigation responded to the findings.
AliExpress said: “AliExpress takes product safety very seriously and maintains strict policies to ensure a safe and compliant online shopping experience. Among these policies is a clear prohibition on the cross-border sale of medications and dietary supplements through our platform. All third-party sellers on AliExpress are required to comply with applicable laws and adhere to our platform rules.
“We have promptly removed the listings flagged by Which?. We are also taking appropriate enforcement actions against the sellers found to be in violation of our policies.”
Amazon said: “Safety is our top priority, and we require all products offered in our store to comply with applicable laws, regulations and Amazon policies. We develop innovative tools to prevent unsafe products from being listed and if we discover a product was undetected by our automated checks, we address the issue immediately and refine our controls.
“We take action to maintain a safe selection for our customers, including removing noncompliant products, and outreach to sellers, manufacturers, and government agencies for additional information, when appropriate. The highlighted items have been removed.”
eBay said: “Consumer safety is a top priority for eBay. These items violate eBay policy and have been removed. We work diligently to prevent and remove unsafe product listings through seller compliance audits, block filter algorithms, AI-supported monitoring by in-house specialists, and close partnerships with regulators. Together, these measures help to prevent millions of potentially unsafe items from being listed each year.
“We are reviewing the wider marketplace to remove any identical listings. We are continually updating filters to prevent bad actors from circumventing our policies. Notably, a number of the listings highlighted by Which? were unavailable for purchase even prior to the investigation being shared with eBay.”
Superdrug said: “Topically applied products that contain melatonin as one of their ingredients are widely available for general sale across the UK. We have contacted the Medicines and Healthcare products Regulatory Agency (MHRA) for clarification on the guidelines for including melatonin as an ingredient within topically-applied products.”
Temu said: “Thank you for bringing this to our attention. Temu prohibits the sale of products containing melatonin and removes any such listings once detected, with penalties applied to sellers for violations.
“Our monitoring systems continuously screen the platform for non-compliant products. As you noted, many of the melatonin products you identified had already been detected and removed before your inquiry. The remaining products were removed on the same day you flagged them, and the sellers were penalised.
“Bad actors will attempt to circumvent controls by deliberately misspelling ingredients or mislabelling products to evade text and image recognition. We have invested heavily in compliance systems combining proprietary technology with expert human review to identify these bad actors and ban them from our platform. We welcome reports of potential non-compliant listings so we can take prompt action.”
