Black market Mounjaro is on the rise ahead of 170% price hike — here’s how to spot fakes

Earlier this month, Mounjaro manufacturer Eli Lilly announced that private UK prescriptions of the weight loss drug would be increasing in price by 170%.

As of September 1, a month’s supply of the highest dose of the weight loss drug will jump from £122 to £330, potentially taking annual costs from £1,586 to a whopping £4,290.

News of the rise sparked a nationwide shortage, as the estimated 500,000 people across the country estimated to pay out of pocket for Mounjaro (which is also available on the NHS) rushed to stock up.

Healthcare professionals shared concerns patients may be pushed towards unsafe methods of obtaining the jabs, with some warning it could lead to a surge in black market sales.

According to a freedom of information request by Chemist4U, 18,300 illegal weight-loss and diabetes medications were seized by Border Force at Heathrow between June 2024 and June 2025 — an issue this price increase is predicted to exacerbate.

‘We’re likely to see more and more people turning to unregulated sellers because the medication may be cheaper,’ said the company’s head of pharmacy, Jason Murphy. ‘Many of these sources distribute counterfeit versions of Mounjaro, which pose serious risks to your health.’

According to the prescriber, counterfeit jabs may include harmful ingredients or other medications, while some don’t actually contain the active drug, tirzepatide. Purchasing from an unregulated source may also violate drug laws, landing you with a fine or even criminal charges.

If you can no longer afford Mounjaro, James recommends speaking with your healthcare provider about an alternative GLP-1 option like Wegovy (which is unaffected by the rise) instead of taking matters into your own hands. If you are tempted to switch to a cheaper supplier though, these three key signs can help you spot – and steer clear of – dangerous fakes.

Cost

While it’s probably not the news you want to hear, Chemist4U says: ‘If the cost of the medication seems too good to be true, it most likely is.’

Do your research on what other providers are charging, and avoid any that seem suspiciously cheap.

Source

‘Wegovy and Mounjaro are prescription-only medicines, and they can only be issued by specialised medical professionals after a consultation,’ James explains.

Regulated providers are required to assess factors like your medical history and weight, but unlicensed sellers – typically operating on social media and in salons – often skip this step, risking patient safety.

For peace of mind, check that the pharmacy you’re buying from is regulated by the General Pharmaceutical Council (GPhC) and the Medicines and Healthcare products Regulatory Agency (MHRA) before you commit.

Appearance

The third indicator to look out for is the appearance of your Mounjaro pen, which James says should ‘come in well-designed packaging with clear, high-quality printing and branding’ and ‘feel solid and well made’.

On the contrary, fakes may have spelling mistakes, blurry printing, incorrect logos, and feel cheap and flimsy, with flaws like uneven colouring, rough edges or loose parts.  

A particularly important thing to look out for is a unique serial number, as counterfeits either won’t have one that matches the manufacturer’s records or won’t have one at all.

And finally, James adds: ‘A real pen should contain liquid that is clear and colourless. Unknown substances in fraudulent pens can be cloudy or tinged with colour, a dead giveaway that they are fake.’

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