THOUSANDS of Brits who use Mounjaro are being urged to check their fat jabs are not fake.
The warning comes after health chiefs discovered a counterfeit version of the ‘’ of was being dished out by an online pharmacy based in .
Credit: Gov.UK
The medicines watchdog said a fake version of Mounjaro KwikPen 15mg, which is also used to treat , has been found after five faulty pens were traced back to one supplier.
All of the fake jabs are labelled with batch number D873576 and were supplied through an online pharmacy called The Private Pharmacy Clinic, a registered UK pharmacy regulated by the General Pharmaceutical Council (GPhC).
In a notice published yesterday, the Medicines Healthcare Regulatory Agency (MHRA) warned patients to immediately stop using any 15mg pen with that batch number and contact the MHRA.
The counterfeit pens appear to contain – the active ingredient in Mounjaro – but the devices are not made to proper safety standards and may not be sterile.
In most cases identified so far, the dose knob came off during use, raising concerns about contamination.
“If its contents are not sterile, there is potential for infection…allergic
reactions may also occur,” it said in the notice.
So far, the MHRA said it has received no reports of serious harm requiring treatment.
However, because the pens may not be sterile, officials warned there is a potential risk of infection.
While the batch number is genuine, it actually corresponds to a real 7.5mg pen, not the 15mg version, meaning all 15mg pens carrying that number are fake.
The regulator is continuing to investigate, and the pharmacy involved has been served with a notice of conditions by the GPhC.
This means it can continue operating but must comply with restrictions while inquiries are ongoing.
Patients who discover their pen is faulty are being urged not to use it.
Credit: Getty
If it is a 15mg pen, they should check the batch number and, if it matches D873576, report it to the MHRA by emailing .
The regulator will then arrange for the pen to be collected.
The alert comes as demand for weight-loss injections such as Mounjaro continues to soar in the UK, with thousands turning to online pharmacies to access the jabs.
Earlier this month, police raided beauty salons flogging illegal fake Mounjaro and Ozempic.
The MHRA has previously annouced that a record number of illegal fat jabs, erectile dysfunction pills and fake drugs were seized last year by UK officials.
Almost 20 million doses of were confiscated by government agencies in 2025.
The combined street value of the products is thought to be worth more than £45 million, according to the health watchdog.
Reports of fake slimming jabs in the UK first emerged in August 2023.
How to check if you have a fake pen
ANYONE using Mounjaro KwikPen 15mg is being urged to check the batch number on their pen or packaging.
The alert applies only to 15mg pre-filled pens labelled with batch number D873576, which you can check at the bottom of the box.
If you have a pen with this number, stop using it immediately and do not attempt to extract any remaining doses.
Patients should report the pen to the Medicines and Healthcare products Regulatory Agency by emailing .
The regulator will arrange collection.
Anyone who has already used the pen and feels unwell including symptoms such as redness, swelling, fever or flu-like illness should seek medical advice urgently.
You can report any side effects to the Yellow Card scheme , which tracks side effects of all medicines and medical devices.
Eze Chidiebere Paul
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