Slimmers were today urged not to bank on Black Friday discounts to buy reduced weight loss injections. 

The once-a-week jabs, made by pharma giants Novo Nordisk and Eli Lilly, are offered on the NHS to help type 2 diabetes patients control their blood sugar levels.

Semaglutide and tirzepatide — the generic name for Ozempic, Wegovy and Mounjaro — also trigger weight loss, earning them praise as a 'miracle' slimming injection.

But huge global demand has seen counterfeit versions flood the market in recent years. 

Health officials have repeatedly warned Britons against buying the jabs on social media and to be aware of scam online retailers posing as pharmacies, over fears they may be selling contaminated versions of the blockbuster injections.

Doctors have also told how patients have suffered seizures and have even been left in life-threatening comas after taking fake versions. 

Now, ahead of Black Friday, experts have urged people not to trust websites flogging the jabs with Black Friday discount codes, over concerns they could be counterfeit. 

Figures suggest that bogus retail sites surge sharply around Black Friday with a 135 per cent rise in fake store domains.

It comes as separate survey data today also revealed that one in five Britons on the jabs have purchased from an unverified 'underground' source, including social media and unlicensed sellers. 

Toby Nicol, CEO of private weight-loss jab provider CheqUp, said: 'Black Friday is a time for deals, but it's also a time when counterfeiters try to exploit consumers, especially in the weight loss injection market. 

'Fake weight loss drugs often originate from unregulated manufacturing operations, where oversight is minimal and quality control can be non-existent. 

'They are only interested in cash, not care. 

'These counterfeit products frequently enter the market through unauthorised online pharmacies or social media marketplaces that bypass regulation and rules.

'There is a real concern that black and grey markets are going to try and exploit vulnerable and desperate patients. 

'Go on any social media site and you can find cowboy operators in minutes — drug dealers, for all intents and purposes — taking advantage of confused patients who can no longer afford treatment but want to continue. 

'As with most things in life, if it's too good to be true, it probably is.'

Under UK law, only pharmacies registered with the General Pharmaceutical Council (GPhC) can prescribe weight loss injections. 

Without GPhC registration, a business is not legally able to dispense medication to patients. 

Such businesses are often run by people with no medical training. 

Mr Nicol also advised patients to check for a batch number and proper medical information leaflet to ensure their weight loss jab is legitimate. 

Real injection pens typically have unique serial number, while fake products either won't have one that matches the manufacturer's records or won't have one at all.

It comes as research by online pharmacy MedExpress, found of the 2,000 weight loss jab patients surveyed, 21 per cent have purchased one from an unverified online or in-person source. 

A further 31 per cent have considered it.

The poll also found men were substantially more likely to buy unverified weight loss drugs, with 27 per cent having bought them, compared to 16 per cent of women. 

Reports of fake slimming jabs in the UK first emerged in August 2023.

Experts have repeatedly said many won't even contain semaglutide or tirzepatide and are often just insulin pens which have been repackaged to look like the real thing, fooling customers.

When patients inject themselves, this insulin surge causes a rapid drop in blood sugar — which can potentially be fatal.

Last year, tests on black-market versions of Mounjaro and Ozempic also found they were laced with rat poison and even cement.

In October, the heartbroken family of a mother of three revealed she died after being injected with a drug bought on the black market. 

Karen McGonigal, 53, died days after she was illegally administered a dose of semaglutide — the powerful ingredient behind Ozempic and Wegovy — in May. 

Her daughters said the 53-year-old had become 'desperate' to lose weight after a long-term relationship ended, and a beautician had offered weight loss injections for £20 each.

Under NHS guidelines only patients who have a body mass index (BMI) of over 35, or a BMI of 30 and at least one weight related health problem like high blood pressure, should be prescribed Wegovy.

While private prescribers aren't bound by this, they still need to follow general professional guidelines and consider national guidance to ensure only patients that need the drug get access to it.