The weight loss jab Wegovy is being made available in the UK as part of a "controlled and limited launch".

From today (September 4) the drug, also known as semaglutide, will be prescribed via specialist NHS weight management services alongside a reduced calorie diet and exercise.

Those eligible should have a body mass index (BMI) over 30 or a BMI of more than 27 and at least one weight-related co-morbidity (when an individual who has obesity develops another health condition due to their weight).

The National Institute for Care and Excellence (NICE) gave Wegovy the green light for NHS use earlier this year.

Its guidance said it should be used for a "maximum" of two years.

Wegovy manufacturer Novo Nordisk said it believes the launch of the drug in the UK "will help provide an additional option to support people living with obesity".

Earlier this year, the government announced a £40 million pilot scheme to increase access to specialist weight management services in a bid to combat obesity, with PM Rishi Sunak describing the drug as a "game-changer".

Read more: Wegovy weight-loss jab to launch in the UK (PA, 2-min read)

Wegovy is usually prescribed as a type 2 diabetes medication that blunts appetite.

It has the same ingredient as Ozempic, which has been causing a stir recently having said to be used by celebrities to manage their weight.

But experts have warned that there could be some side effects to using the drug as an aid to weight loss, without medical supervision, with Dr Amir Khan previously appearing on both GMB and Lorraine to issue some advice.

Here's everything you need to know about Wegovy or Ozempic in 10 points.

What is Ozempic? Ozempic, Ryblesus and Wegovy are all brand names for a compound called semaglutide. The drug is typically used as a diabetes medication, can be prescribed in various doses and can be in the form of a weekly injection – administered in the stomach, thigh or arm – or a daily oral tablet.

The drug reportedly reduces appetite. "It is a hormone that our guts naturally produce," explained Dr Amir Khan on ITV's Lorraine. "It sends messages up to the pancreas to start producing insulin. But one of the side effects is it slows down the movement of food in the gut so you stay fuller for longer and you don't have much of an appetite. That means you eat less which results in weight loss."

The drug is rumoured to be secretly used by many Hollywood stars. At the Critics Choice Awards earlier this year Chelsea Handler hinted that many celebrities were taking the injectable. "Like when celebrities joke they lost weight by drinking water, but really it's because everyone's on Ozempic," she joked. "Even my housekeeper's on Ozempic."

Searches on social media also link the Kardashians with the drug. But despite Kim Kardashian never confirming her use of Ozempic and her sister, Khloe, issuing a statement denying that she'd used it, it continues to clock up hashtags.

Other celebrities have openly admitted using the drug as a weight loss aid including Elon Musk, who told Twitter he'd tried it, saying the once-weekly injectable was his secret weapon for being "down 30lbs". Jeremy Clarkson also discussed using the drug in a bid to lose weight.

It's causing a buzz online. Thanks to its reputation as the weight loss drug du jour, Ozempic is quickly clocking up views and shares on social media. On TikTok the hashtag #ozempic already has 1.1 billion views and counting, while Instagram is littered with users sharing their "Ozempic journey" to weight loss.

The drug was hailed a potential 'game changer' during an official UK study. A University College London study, published in The New England Journal of Medicine, found just over a third (35%) of people who took it for obesity lost more than a fifth of their total body weight.

Ozempic does come with risks. Dr Amir Khan warned that side effects could include "nausea, vomiting, feeling bloated, diarrhoea, but in some, more serious, cases it can cause inflammation of the pancreas, that's pancreatitis."

He added it can also cause gall bladder problems. "It can even cause kidney failure," he said, "so really it should only be available on prescription. I do prescribe it to my patients living with type 2 diabetes, but it's very carefully monitored. It is not just given online."

Eating disorder charities also have concerns. “Weight-loss medications like semaglutide can be extremely attractive to people with eating disorders as they appear to provide quick results," Tom Quinn, Beat’s director of external affairs, explains.

“However, these medications can be very dangerous as they can worsen harmful thoughts and behaviours for those unwell, or contribute to an eating disorder developing for someone who is already vulnerable.”

Doctors say weight loss medications aren't a magic cure. The NHS advises speaking to your GP for advice about losing weight safely "by eating a healthy, balanced diet and doing regular physical activity".

They can also let you know about other useful services, such as local weight loss groups (either provided by the NHS or your local council, as well as private clubs that you pay for) and "exercise on prescription" (where you're referred to a local active health team for sessions with a qualified trainer).

Additional reporting PA.