Weight loss medication complete guide: From Wegovy to Mounjaro

Weight-loss drugs medicine
Several weight-loss drugs are now available and new, better versions are being researched all the time

The new generation of weight-loss drugs were initially developed to treat diabetes and work by mimicking a hormone that regulates insulin levels and appetite. When celebrities started shedding pounds with private prescriptions for the diabetes drug Ozempic, the race was on to make them more widely available for weight loss.

There are now several different drugs including tirzepatide, Ozempic, Saxenda and Wegovy available, and now a new drug, retatrutide – dubbed the “Godzilla” – which claims to be more powerful than its predecessors, cutting body weight by a quarter.

So are you the right candidate, how much do the drugs cost, and which one is right for you, if at all? Here’s everything you need to know.

A round-up of the latest weight loss drugs: 

What is the difference between weight-loss jabs and pills?

The new GLP-1 hormone-mimicking weight-loss drugs are given by injection. Wegovy is also available in pill form, known as Rybelsus, but is not as well absorbed by the body as when given with a jab.

Dr Luke Pratsides is an NHS GP and also head of medical at Numan, an online men’s healthcare company that will be offering Wegovy as part of its weight-loss treatment programme.

He says: “Wegovy and Ozempic are available in a tablet form Rybelsus, but you need higher doses to get the same effect, as it’s not as well absorbed by the gut as it is when injected into fat through the skin.

“The worry is that if you are increasing the dose then you might be increasing the potential risk of side effects, so an injection is preferable.”

Orlistat, an older weight-loss drug, is given in tablet form. Dr Pratsides explains: “This medication works in a different way by blocking fat absorption, so needs to get to the gut to work effectively. However, the new GLP-1 drugs are far more effective than Orlistat.”

How much do weight-loss medications cost in the UK and US?

In the UK, some weight-loss medications are available on the NHS, provided you meet the criteria for the specific drugs.

The drugs are also available privately and costs vary widely, ranging from between £150-£300 a month. In the US, the list cost for the drugs starts at about $800 per month.

Some insurers will cover the drugs, so the price for the patient will depend on their individual policy. However, increasingly insurers are refusing to foot the steep bills.

As more drugs become available and patents expire, experts believe the price will drop in the same way as it eventually did for statins.


Launched in the UK in 2023

A selection of injector pens for the Wegovy weight-loss drug
A selection of injector pens for the Wegovy weight-loss drug

What is Wegovy?

“Wegovy is a brand name of the drug semaglutide,” explains Dr Saira Hameed, a consultant in endocrinology and diabetes at Imperial College Healthcare NHS Trust and the author of The Full Diet.

Wegovy is the same drug as Ozempic, but Wegovy is available in higher doses and is designed specifically for weight loss.

Does Wegovy work?

Wegovy is designed to suppress your appetite, so you eat less. It mimics the action of a gut hormone called GLP-1, which is released after eating, and slows down the movement of food in your gut, so you stay full for longer.

“These fullness hormones send a signal from the gut to the brain to indicate satiety,” says Dr Hameed. “The result is that people feel full even if they haven’t eaten, and when they do eat, they are satisfied with a smaller amount of food.”

Is it safe/FDA-approved?

Wegovy is approved in the United States by the Food and Drug Administration (FDA) for chronic weight management in adults with obesity or who are overweight with at least one weight-related condition (such as high blood pressure, Type 2 diabetes, or high cholesterol).

The most common side effect is nausea. Others include vomiting, abdominal pain, constipation, diarrhoea, acid reflux, wind, headache and fatigue. These tend to occur initially – for 95 per cent of people, they disappear within a couple of months.

More serious risks include gallstones and pancreatitis. The drugs should not be used during pregnancy – or by women trying to get pregnant – or by those who are breastfeeding.

Am I the right candidate and how quickly will I see results?

In a clinical trial, published in the New England Journal of Medicine in 2021, Wegovy-treated participants lost about 2st 5lb (15kg) over a 68-week period. This equated to an average of about 15 per cent of their body weight.

But there is a caveat. When people stop taking Wegovy, they tend to put the weight back on.

“A subset of people in the trial were followed up for a further year,” says Dr Hameed. “Twelve months later, they had regained, on average, two-thirds of the weight they had lost on the drug.”

In the latest research, these weight loss jabs have also been found to cut the risk of heart death by a fifth, a study has found, with medics calling for them to be prescribed like statins.

Will my medical insurance cover Wegovy and is it available on the NHS?

In the US, many private insurers cover Wegovy, but it will depend on your individual plan. Medicaid also covers Wegovy, typically for patients with a BMI of 30 or higher or a BMI of 27 or higher with at least one weight-related medical condition.

In the UK, the drug is available on the NHS via specialist NHS weight management services after a referral from your GP.

How is it taken?

Once a week, with a self-administered injection. The National Institute for Health and Care Excellence (Nice), the medical treatment regulator for England, has approved its use for a maximum of two years, at a dose of up to 2.4mg.


One of the newer generation, approved for use by Nice in England

A box of Mounjaro, a tirzepatide injection
A box of Mounjaro, a tirzepatide injection

What is tirzepatide/Mounjaro?

“This is a really impressive medication,” says Dr Alex Miras, a consultant in endocrinology at Imperial College London. “What makes it unique is that it combines synthetic analogues of two hormones – GLP-1 and GIP – which stimulates insulin secretion.”

Both, he explained, are naturally occurring hormones that we all produce in our intestines when we eat. Tirzepatide is currently sold under the brand name Mounjaro.

Does tirzepatide work?

The combination of the two hormones in the drug helps to suppress appetite and also to control blood sugar.

Dr Miras says: “Randomised control clinical trials have shown that it causes about 22 per cent weight loss. We’re getting into weight-loss territories that only bariatric surgery is able to achieve. That’s why we’re so excited.”

Is it safe/FDA-approved?

“In the US, tirzepatide has already been approved for adults with diabetes, because it causes very profound reductions in glucose,” says Dr Miras.

Tirzepatide is currently being assessed in the US for the treatment of obesity, and some private clinics are prescribing it off-label for weight loss.

Clinical trials have compared its effect on people with diabetes to those of Ozempic. According to Dr Miras: “What they’ve found is the side effects are very similar: nausea, constipation, diarrhoea.”

Am I the right candidate and how quickly will I see results?

A recent trial found tirzepatide helped overweight or obese patients lose up to almost a quarter of their body weight, or 22 per cent, after 17 months compared to a 2 per cent weight loss with a placebo.

Will my medical insurance cover tirzepatide and is it available on the NHS?

Nice has now approved tirzepatide issuing draft guidance that very obese people - with a body mass of at least 35 - should be prescribed it.

In the US, as Mounjaro is currently only approved to treat adults with Type 2 diabetes, your insurance policy may cover it but only if you have diabetes. You may be able to obtain a private prescription for weight loss, but without insurance, costs are in the region of $1,000 for four doses.

How is it taken?

An injection, once a week.


The one celebrities have been getting

A pharmacist displays boxes of Ozempic
A pharmacist displays boxes of Ozempic

What is Ozempic?

Ozempic is the same drug as Wegovy, semaglutide, but administered at a lower dose and is specifically licensed to treat Type 2 diabetes only.

Does Ozempic work?

“Because Ozempic hasn’t been trialled for weight loss, it hasn’t been licensed for this use,” says Dr Hameed. As it is the same drug as Wegovy, it works in the same way.

Is it safe/FDA approved?

Ozempic is approved by the FDA for use in adults with Type 2 diabetes. However, private clinics have been prescribing it off-label for weight loss, which is how celebrities started taking it.

Am I the right candidate and how quickly will I see results?

Ozempic produces similar results to Wegovy.

Will my medical insurance cover Ozempic and is it available on the NHS?

In the US, Ozempic is covered by some insurers, depending on your plan. It is available on the NHS for Type 2 diabetes.

Private clinics in the UK were told to stop prescribing Ozempic for weight loss as it was creating shortages for diabetics. Wegovy is now licensed to be prescribed for weight-loss instead.

“Ozempic is licensed in the UK, on the NHS, for the treatment of Type 2 diabetes,” says Dr Hameed. “It’s usually only prescribed when tablets have not sufficiently controlled blood glucose levels.

How is it taken?

Also as a self-administered injection, at a dose of up to 1mg once a week.


The older option

Orlistat is taken in tablet form
Orlistat is taken in tablet form

What is Orlistat?

A drug that has been in use since the Nineties, “Orlistat works by reducing the amount of fat that people absorb from their gut when they eat,” explains Dr Miras.

Does it work?

Orlistat works by expelling some of the fat people take in from meals. According to Dr Miras: “The resulting diarrhoea is so unpleasant, it effectively punishes you for having eaten fat. It makes the person learn to cut down on the fat in their diet.

“When that happens, and there are people who do that, then these people do well with their weight loss. However, the weight loss is small, and the side effect – diarrhoea – is pretty severe.”

Is it safe/FDA approved?

Orlistat is safe to use and approved by the FDA. Side effects can be unpleasant – if you eat fatty food, you’re likely to suffer from offensive-smelling diarrhoea.

Will my medical insurance cover Orlistat and is it available on the NHS?

The NHS will prescribe Orlistat to people with a BMI of 30 or more, or those with a BMI of more than 28 who also have a risk factor such as Type 2 diabetes, hypertension or familial high cholesterol. Orlistat is covered by medical insurance in the US, depending on your plan.

How is it taken?

In tablet form, before meals.


The drug that’s been around for a while


What is it?

Saxenda (generic name liraglutide) is an antidiabetic medication used to treat Type 2 diabetes and chronic obesity.

Does it work?

“Like Wegovy and Ozempic, Saxenda also mimics the hormone GLP-1, leading to a feeling of fullness,” notes Dr Hameed. But it has a shorter “half-life” than Ozempic and Wegovy and has to be taken every day.

Is it safe/FDA approved?

Saxenda is approved by the FDA for chronic weight management in adults with a BMI over 30. Side effects are similar to Wegovy and Ozempic and include tiredness, dizziness, stomach problems and gallstones.

Am I the right candidate and how quickly will I see results?

Trial data suggest that people taking Saxenda for 56 weeks lose, on average, 1st 4lb (8.4kg), or 8 per cent of their body weight.

As with Ozempic and Wegovy, people put the weight back on when they stop: in this case, an average of 2.9kg (6lb) after 12 weeks.

Will my medical insurance cover Saxenda and is it available on the NHS?

Saxenda is covered by many insurances and is available on the NHS.

In the UK, it is prescribed via specialist NHS weight-loss services for people with a BMI of 35 or above, who have prediabetes and at least one cardiovascular risk factor, such as hypertension or high cholesterol.

You have to do “homework” before you are prescribed it. According to Nice guidance, you must lose at least 5 per cent of your body weight after 12 weeks on the full dose in order to continue with the medication.

How is it taken?

Also as a self-administered injection, at a dose of up to 3mg every day.


The newest drug on the block


What is it?

Like Ozempic and Wegovy it mimics the action of appetite-suppressing hormones, but the main difference is that it also targets a third hormone which has the power to speed up metabolism, spurring the body to burn more fat.

Does it work?

Billed as the “Godzilla” of these types of medication, the weekly retatrutide jab claims to have  a “triple whammy” effect –and latest trials have shown the drug has helped obese people shed on average 60lb (4st 4lb or 27.2 kg) in just 48 weeks.

Is it safe/FDA approved?

Phase 3 trials are now underway to see how much more weight users can drop as well as assessing side effects and checking for more serious problems. These will publish results in 2026.


Weight loss pills
Weight loss pills

What is it?

A weight-loss drug that works in the same way as Wegovy, stimulating insulin secretion, but is taken in tablet form once a day, rather than as an injection.

Does it work?

Phase 2 clinical trials demonstrated that the pill worked to reduce the weight of obese patients by as much as 15 per cent over a 36-week period.

Is it safe/FDA approved?

Phase 3 clinical trials have been launched. Results are expected in the second half of next year, after which it would still need to be licensed and approved for use in the UK.

The natural over-the-counter options

If you would rather pop down to Boots or Holland & Barrett, which over-the-counter options are the most promising?

Green coffee bean extract

In pill or powder form, this is currently popular and, says Dr Hameed, it “probably has a small effect on weight loss by increasing metabolism, similar to drinking caffeinated drinks”.

She added: “A few short-term randomised clinical trials show it might help with losing a few pounds, but more robust, longer-term studies are definitely needed before any definitive conclusions can be drawn.”

Raspberry ketones

Dr Hameed said: “Some in-vitro cellular experiments [in test tubes], as well as rodent studies, suggest that they may support weight loss by reducing food consumption, as well as increasing body-fat breakdown.

“However, there is no good evidence from human studies to show that these supplements help with weight loss.”

Green tea extract

This has been linked to liver damage and even liver failure. When it comes to supposed weight-loss properties, “the data are quite promising for mice,” according to Dr Duane Mellor, a senior teaching fellow at Aston Medical School and a spokesman for the British Dietetic Association.

“So if your pet rodent has a weight problem, you might be on to something. But for humans? The data are pretty limited.”