Safety guide
Fake Mounjaro in the UK: How to Check Your Pen and Known Alerts
Falsified Mounjaro pens have reached the UK supply chain, including a batch of counterfeit 15mg KwikPens identified by the MHRA in February 2026. This guide explains how to check the pen you have, what the known alerts cover, what to do if yours matches, and how fakes get into circulation in the first place.
Key facts
- In February 2026 the MHRA confirmed falsified Mounjaro 15mg KwikPens in the UK supply chain, labelled 15mg with batch number D873576.
- Genuine 7.5mg pens also carry batch D873576. That batch number alone does not mean a pen is fake; it is 15mg plus D873576 that is affected.
- Check the strength and the batch number on both the pen and the carton before you use it.
- If yours is 15mg with batch D873576, do not use it. Report it to the MHRA and contact the pharmacy that supplied it.
- The pens were traced to one named pharmacy. No pharmacy listed on Monj was involved.
- Most fakes reach patients through social media, marketplaces and copycat websites rather than registered pharmacies.
- Report any suspected falsified medicine through the MHRA Yellow Card scheme, which covers fake and substandard products as well as side effects.
How to check the pen you have
- Read the strength on the pen and on the carton. They must match each other and match your prescription label.
- Find the batch number, printed on the carton and on the pen label, usually alongside the expiry date.
- Compare against the known alert below. If your pen is 15mg with batch D873576, do not use it.
- Look at the pen itself. The dose knob should be firmly attached and turn smoothly. Anything loose, rattling or detaching is a reason to stop.
- Look at the solution. It should be clear and colourless. Cloudy, discoloured or containing particles means do not use it, whatever the batch.
- Check the packaging. Genuine cartons carry the manufacturer’s details, a UK patient information leaflet and a tamper-evident seal. Misspellings, poor print quality, missing leaflets or a leaflet in another language are all warning signs.
- Check where it came from. A pen supplied by a GPhC-registered pharmacy after a consultation is very unlikely to be falsified. A pen bought through social media, a marketplace or a website you cannot verify is the highest-risk route there is.
If anything is wrong, do not inject. Photograph the pen, the carton and the batch number, keep everything, and contact the pharmacy that supplied it the same day.
Known UK alert: falsified 15mg KwikPens, February 2026
On 24 February 2026 the MHRA issued a Drug Safety Update after identifying counterfeit Mounjaro 15mg pre-filled KwikPens in the UK supply chain. The regulator uses the formal term “falsified”, meaning a product that deliberately misrepresents its identity, composition or origin.
| Pen | Status |
|---|---|
| 15mg, batch D873576 | Affected by the alert. Do not use. |
| 7.5mg, batch D873576 | Genuine when supplied through a regulated UK pharmacy. The alert does not apply. |
| Any other strength or batch | Not covered by this alert. Apply the general checks above. |
What the MHRA found: some of the affected 15mg pens failed mechanically, including the dose knob detaching. Manufacturing standards could not be verified. Testing suggested the pens contained tirzepatide, but the regulator could not confirm they were sterile or safely made. At the time of the alert no confirmed cases of serious harm requiring treatment had been reported.
The pens were supplied through The Private Pharmacy Clinic, operated by Simply Meds UK Ltd (GPhC registration 9012397), the only pharmacy named in the published regulatory update. That pharmacy is not listed on Monj or on our sister sites, and no pharmacy we list has been connected to this alert.
If you think your pen is fake
- Do not use it. Keep the pen, the carton and the leaflet.
- Report it to the MHRA through the Yellow Card scheme, which accepts reports of suspected falsified or substandard medicines, or contact the MHRA directly.
- Contact the pharmacy that supplied it and ask for a replacement or refund. A registered pharmacy is responsible for what it dispenses.
- If you have already injected from it and feel unwell, contact NHS 111 or your GP, and report it as above. Seek urgent help for anything severe.
- Raise a concern with the GPhC if a registered pharmacy supplied it.
- Tell Monj so we can check our listings and warn others.
How fakes get into circulation
Two routes account for almost all of it. The first, and by far the commonest, is direct sale outside the regulated system: social media accounts, messaging apps, marketplaces and websites that take payment without a prescription. Nothing about that supply is checked by anyone.
The second, rarer and more serious, is a falsified product entering the legitimate supply chain, which is what the February 2026 alert describes. This is why regulated pharmacies are required to source only through authorised wholesalers and why the MHRA acts quickly when a batch is identified.
The practical defence is the same in both cases: buy only from a GPhC-registered pharmacy after a real consultation, treat a price far below the regulated market as a warning sign, and check the pen when it arrives. Our guides to checking a pharmacy is genuine and spotting a fake pharmacy cover the checks in full.
Common questions
Is my Mounjaro pen fake if it has batch D873576?
Only if it is also labelled 15mg. Genuine 7.5mg pens carry that batch number legitimately and are not covered by the MHRA alert. Check the strength and the batch together.
How can I tell if Mounjaro is genuine?
Check that the strength on the pen matches the carton and your prescription label, that the batch number is not on a published alert, that the dose knob is firmly attached, that the solution is clear and colourless, and that the carton has a UK leaflet and an intact tamper seal. Above all, check it came from a registered pharmacy.
What should I do with a pen I think is counterfeit?
Do not use it. Keep it and the packaging, report it to the MHRA through the Yellow Card scheme, and contact the pharmacy that supplied it for a replacement or refund.
Were any pharmacies listed on Monj affected by the 2026 alert?
No. The MHRA named one pharmacy, The Private Pharmacy Clinic, operated by Simply Meds UK Ltd. It is not listed on Monj or our sister sites and no listed provider was connected to the alert.
Are fake pens dangerous even if they contain tirzepatide?
Yes. Testing of the affected 15mg pens suggested tirzepatide was present, but the MHRA could not confirm sterility, dose accuracy or manufacturing standards, and some pens failed mechanically. An unverified injectable is a risk regardless of what it appears to contain.
Where do most fake weight loss injections come from?
Sales outside the regulated system: social media, messaging apps, marketplaces and websites that supply without a prescription. Buying from a GPhC-registered pharmacy after a consultation removes almost all of that risk.
Sources
- MHRA. Falsified Mounjaro KwikPen 15mg pre-filled pens, Drug Safety Update, February 2026.
- General Pharmaceutical Council. Register entry and enforcement record, The Private Pharmacy Clinic (9012397).
- MHRA. Yellow Card scheme, reporting suspected falsified or substandard medicines.
- Eli Lilly and Company. Mounjaro KwikPen patient information leaflet, electronic medicines compendium.
With thanks to the r/mounjarouk community and its moderators, whose reporting helped spread the February 2026 warning quickly.
Monj is an independent price information service operated by Medstack Ltd. It does not sell, prescribe or supply medicines and does not give medical advice. If you are unsure whether a pen is genuine, do not use it and contact the pharmacy that supplied it.
