A GP has revealed the six biggest mistakes people make while taking revolutionary weight-loss jabs.

Sold under the brands Wegovy and Mounjaro, as well as the off-label prescriptions of diabetes drug Ozempic, the injections have become an increasingly popular option for people needing, or wanting, to lose weight.

At least half a million NHS patients and some 15million in the US are now thought to be using the jabs, which can help patients shed up to 20 per cent of their body weight in just a handful of months.

But family medic Dr Donald Grant, from The Independent Pharmacy, said there were a number of errors people could make when starting out on the drugs.

He warned that not only could these mistakes derail patients' weight-loss plans, some could even land them in A&E.

One of the most common — and serious — mistakes slimmers make is taking too much too soon, Dr Grant said.  

Both Wegovy and Mounjaro patients typically start on weekly jabs, either 0.25mg or 2.5mg respectively for each drug, for four weeks, before increasing the dosage in stages from there. 

While Dr Grant said patients may be tempted to up the dosage under the logic of 'more is better', this was false and potentially dangerous.

'Contrary to popular belief, taking a higher dosage of the medication does not necessarily mean quicker results,' he said. 

'Our bodies need time to adjust to the treatment, so beginning on a high dosage could greatly increase the intensity of symptoms such as headaches, fatigue and nausea.'

It could also increase the risk of rarer but more serious side effects like pancreatitis, a serious inflammation of the pancreas, and hypoglycaemia, a medical term for potentially dangerous blood sugar levels.

Dr Grant added: 'I advise anyone on the treatment to discuss their dosage with a licensed health professional, rather than increasing the strength on their own accord.'

Another mistake was taking a weight-loss drug without actually acquiring it legitimately. 

Doctors have long warned they are seeing increasing numbers of slim women needing emergency treatment after obtaining the drug from chemists by lying about their weight.

It was recently revealed that a 16-year-old girl was able to buy Wegovy at Boots as part of an undercover sting. 

Dr Grant said patients obtaining the drug from unreliable sources were taking additional risks.

'A common mistake that’s unfortunately being seen more and more is the amount of Brits obtaining these treatments through illegal measures - such as fraudulent sites or social media,' he said. 

'This can be an incredibly dangerous process as these organisations aren’t regulated with the same level of health safety protocols as proper healthcare establishments.

'As a result, they could have foreign ingredients that could impact well-being.'

Under official guidelines, only patients who have a body mass index (BMI) of over 35, or between 30 to 34.9 and meet the criteria for referral to a specialist weight management service, should be prescribed Wegovy.

Mounjaro has similar restrictions under NHS guidelines, with patients needing a BMI of more than 35 and at least one obesity-related health problem. 

Ozempic, on the other hand, is a diabetes medication but has been prescribed for weight loss 'off label'. 

Dr Grant said another mistake patients frequently make is feeling they can 'eat whatever they like' while on the medications. 

'Sadly, this is simply not the case and eating too many processed or sugary foods could cause blood sugar spikes, leading to increased appetite, bloating and fatigue,' he added.

'People should prioritise a well-balanced diet of proteins, fibre and other key nutrients. 

'Although these treatments impact appetite, it’s still important to draw up a dietary plan that includes all the key foods.'

In a similar vein, Dr Grant said patients should also ensure they stay hydrated.

'Not doing so risks increasing the intensity of side effects, which can be difficult to manage - particularly for people still adjusting to the medication,' he said. 

'Water is also a key component for weight loss, not drinking enough can slow down progress and lead to dehydration.' 

On side effects in general, Dr Grant also said it was critical that patients don't ignore them and inform their medical team of any issues so they can help. 

'By keeping your GP up to date with any symptoms, they can provide tailored advice and guidance to lessen side effects and restore a better quality of life,' he said.

'Common side effects include diarrhoea, nausea and fatigue, while less common symptoms range from shortness of breath to abdominal pain.'

'If any side effects persist, I strongly recommend seeking medical attention for further advice.'

Dr Grant's final tip was to ensure you don't skip doses. 

'This can halt progress, stopping people from reaching their weight loss goals, as it can increase appetite and reduce the overall effectiveness of the treatment,' he said. 

'Therefore, before beginning any weight loss medication, be sure to consider the long-term costs and reordering processes.'

Weight loss jabs work by mimicking a natural hormone that makes people feel full, reducing their appetite and helping people lose weight.

While hailed as a breakthrough in tackling obesity, the drugs have also been shown to significantly reduce the risk of heart attacks and strokes.

However, side effects are wide-ranging, from nausea and abdominal pain to severe digestive issues, bone pain and a potential higher risk of thyroid cancer.

A Mail on Sunday investigation earlier this year also revealed almost 400 patients had been hospitalised — some with life-threatening complications — since the rollout of the jabs in the UK.