Patient guide
Fake and unlicensed weight-loss injections: the risks and what to do
Demand for weight-loss injections has created a market for counterfeit and unlicensed products. These can contain the wrong dose, the wrong substance or contaminants. This guide explains the risks, how to reduce them and what to do if you have used one.
Last checked: 2026-10-03
Key facts
At a glance.
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Regulator warnings
The MHRA has issued warnings and taken enforcement action against illegal supply of weight-loss injections.
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Research peptides
Products labelled for research use are not licensed medicines and are not intended for human injection.
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Real harm
Reports have involved severe hypoglycaemia, hospital admissions and infection from unregulated products.
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Reporting
You can report suspected fake medicines and adverse reactions to the MHRA.
What counts as fake or unlicensed
Counterfeit products imitate licensed pens but may contain a different amount of active ingredient, none at all or something else. Unlicensed products include substances sold as peptides, research chemicals or compounded injections, which have not been assessed by the MHRA for safety, quality and effectiveness. Genuine medicines are made under controlled standards and tracked through licensed supply chains.
Why it is dangerous
Injecting an unknown product risks serious harm. A pen that contains insulin instead of the expected medicine can cause dangerously low blood sugar. Contaminated or non-sterile products can cause infection. An incorrect dose can cause severe vomiting and dehydration. Because these products are made without quality control, the risks are not predictable.
Warning signs
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Offered through social media, messaging apps or marketplaces rather than a registered pharmacy.
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No prescription or consultation requested, or only a short form.
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Prices far below what registered services charge.
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Packaging with spelling mistakes, unusual labelling or no batch number.
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Sold as "research use only", "peptide" or "compounded" injections.
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Pens or vials sold without a proper patient information leaflet.
What the MHRA recommends
The MHRA advises obtaining medicines only from a registered pharmacy, checking prescribers on their professional register and not buying prescription-only medicines from sellers who do not ask for a prescription. It has also asked health professionals and the public to report suspected counterfeit products and side effects through the Yellow Card scheme.
If you have already used one
Stop using it and keep the packaging and any remaining product, because the batch details help investigators and clinicians. Do not share the remaining pens with anyone else. If you feel unwell, seek medical advice, and call 999 or go to A&E if you develop confusion, sweating and shaking, drowsiness, severe vomiting, difficulty breathing, a spreading rash or severe abdominal pain. Tell clinicians exactly what you injected and where it came from. Report it through the Yellow Card scheme.
Safer alternatives
If cost or availability is a barrier, talk to your GP or pharmacist about options, including NHS weight-management services, lower-cost licensed medicines and non-drug approaches. An honest conversation is better than risking an unregulated product. Pharmacists in particular are used to these conversations and can often explain what is licensed, what is not and what a reasonable alternative might be, without any judgement about how you came to ask.
Frequently asked
Questions people ask.
Quick, plain-English answers to the questions we hear most.
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How can I tell if a pen is genuine?
It is hard to tell by looking. The safest approach is to obtain it from a registered pharmacy on a valid prescription.
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Are overseas pharmacies safe?
Some are legitimate, many are not. If it is not a UK-registered pharmacy, protections are limited and the product may not be authorised here.
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What are research peptides?
Substances sold for laboratory use. They are not approved medicines, and selling them for human use is not lawful.
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Is "compounded" the same as licensed?
No. Compounded or unlicensed preparations have not gone through the same assessment as licensed medicines.
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Can I report a seller?
Yes. The MHRA takes reports about suspected illegal sales of medicines.
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What are signs of low blood sugar after injecting?
Shakiness, sweating, hunger, confusion, palpitations and drowsiness. Take fast sugar if you can and seek urgent help if symptoms are severe.
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Will a GP treat me if I have used one?
Yes. Clinicians will treat any harm and need to know what you used. They are not there to judge you.
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Does the NHS ever supply these medicines?
Yes, to people who meet eligibility criteria through NHS services, with no charge for the medicine itself beyond any standard prescription rules.
Where this comes from
Sources and checking.
This guide is for information, not medical advice.
Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.
Published 2026-10-03, next review 2027-10-03.
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MHRA drug safety updates and Yellow Card scheme information (gov.uk/mhra)
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General Pharmaceutical Council, guidance for registered pharmacies providing services at a distance, including online (pharmacyregulation.org)
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NHS website, Obesity and weight-loss medicines pages (nhs.uk)