What should you know about weight-loss medication?

This page gives general, neutral information, not personal medical advice. Never start, change or stop a medicine without talking to your doctor. Approval, availability and reimbursement differ by country. Information checked in October 2026.

Where does Obesity Foundation stand?

Obesity Foundation does not recommend or promote weight-loss medication. We explain what these medicines are, because many people ask about them and deserve honest facts. Whether medication is right for you is something to discuss with your own doctor; that decision is yours. Our own focus is good food, appropriate exercise at the right level and walking, together with sleep and support.

What is weight-loss medication and how does it work?

Most weight-loss medicines used today copy the action of GLP-1, a hormone your gut releases after eating, which tells the brain you are full. They reduce appetite and slow the emptying of the stomach. Semaglutide and liraglutide act on the GLP-1 receptor. Tirzepatide acts on two hormone receptors, GIP and GLP-1.

These medicines also lower blood sugar, which is why some were first developed for type 2 diabetes. Older medicines work in other ways, for example by blocking the absorption of part of the fat in food.

Medication does not replace good food, movement and sleep. Read more about the biology of appetite on genetics and biology.

Which medicines are approved?

As of October 2026, the main approved weight-loss medicines in the European Union (EU) and the United States (US) are listed below. In the trials, everyone also received advice on food and physical activity. Results differed widely between people, and the effect lasted only as long as people kept taking the medicine.

Some notes on this table:

• Orlistat blocks the absorption of part of the fat in food. A lower dose is sold without prescription in some countries.
• For naltrexone/bupropion, the EU medicines agency (EMA) has completed a safety review. Treatment should stop if people have not lost at least 5 percent of their weight after 16 weeks, or do not maintain that loss after one year.
• Setmelanotide is approved for a few rare genetic forms of obesity, confirmed by genetic testing.

What does the WHO guideline say?

WHO has published its first guideline on GLP-1 medicines for obesity. It makes two conditional recommendations: that adults living with obesity, except pregnant women, may use these medicines as long-term treatment, and that people who use them may be offered intensive support with diet and physical activity.

WHO calls the recommendations conditional because long-term data, costs and fair access are still uncertain. It also notes that, even in the best case, production could cover fewer than 10 percent of people living with obesity.

Who can be prescribed these medicines?

Most weight-loss medicines are approved for adults with a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related health problem, such as type 2 diabetes, high blood pressure or sleep apnoea. Some are also approved for adolescents from 12 years.

National rules on who can get them, and whether costs are covered, are often stricter and differ by country. Only a doctor can prescribe them, after looking at your health, your other medicines and your wishes. See BMI and waist size and clinical obesity for how doctors assess obesity.

What are the side effects?

Side effects are common, especially in the digestive system. Across trials of GLP-1 medicines, 28 to 44 percent of people had nausea, 21 to 30 percent diarrhoea and 11 to 24 percent constipation. Vomiting, heartburn and tiredness also occur. These effects are most common when starting or increasing the dose.

Rare but serious risks include:

• Inflammation of the pancreas (pancreatitis): seek urgent help for severe stomach pain that spreads to the back and does not go away.
• Gallbladder problems, such as gallstones.
• Dehydration from vomiting or diarrhoea, which can affect the kidneys.
• Sudden loss of vision from a condition called NAION: the EMA considers this a very rare side effect of semaglutide, affecting up to 1 in 10,000 users. Contact a doctor urgently if your eyesight suddenly gets worse.
• Risks during anaesthesia: because the stomach empties more slowly, always tell your surgeon and anaesthetist that you use these medicines.

In the US, the labels of semaglutide, liraglutide and tirzepatide also warn against use by people with a personal or family history of medullary thyroid cancer or the related MEN2 syndrome.

Do you lose muscle with these medicines?

Yes, part of the weight lost is lean tissue, including muscle, as happens with any large weight loss. Good food with enough protein, daily walking and muscle-strengthening exercise at least twice a week help protect muscles and bones. Our free workouts include strength exercises at every level. See lifestyle treatment for practical tips.

What happens when you stop?

When people stop these medicines, most of the lost weight usually returns, often within one to two years. In the STEP 1 extension, people regained about two-thirds of their weight loss in the year after stopping semaglutide. A recent analysis in The BMJ of 37 studies estimated that weight returns to the starting level about 1.5 years after stopping the newest medicines, and that benefits for blood sugar and blood pressure also fade.

Weight regain is not a personal failure. It reflects how strongly the body defends its weight. Talk to your doctor before stopping, and read more about weight regain.

What about costs and access?

Costs and access differ a lot between countries. In some places weight-loss medicines are reimbursed only for certain groups, in others not at all, and supplies have at times been limited. Because weight usually returns after stopping, the costs often continue for as long as the medicine is used. Ask your doctor or health insurer what applies where you live.

What is still unknown?

The newest medicines have only been used widely for a few years, so data on use over many years are still being collected. Questions remain about long-term safety, about what happens with repeated stopping and restarting, and about effects in older people and adolescents. This is one reason why WHO made its recommendations conditional.

Can you use them during pregnancy?

No, obesity medicines should not be used during pregnancy or while breastfeeding, because there is not enough safety data. If you could become pregnant, use reliable contraception. The UK medicines regulator advises stopping semaglutide at least two months and tirzepatide at least one month before trying to conceive.

Tirzepatide can make the contraceptive pill less effective, so an extra or non-oral method is advised, especially after starting or increasing the dose. If you become pregnant while using one of these medicines, contact your doctor straight away. See obesity and pregnancy.

How do you avoid fake medicines?

Only use obesity medicines prescribed by a doctor and supplied by a licensed pharmacy. The European Medicines Agency (EMA) has warned about falsified semaglutide pens, including fake versions of a diabetes pen (Ozempic), found in several countries. Fake products may contain no active substance, the wrong dose or a different substance, which can be dangerous.

Do not buy from social media, beauty salons or websites that sell without a prescription, and do not use powders that you have to mix yourself. Report suspicious products to your national medicines authority.

What Obesity Foundation offers: food, walking and exercise

Whatever you and your doctor decide about medication, the basics of good health stay the same, and they are where we can help. Everything we offer is free.

• Walking. Walking is free, needs no equipment and is gentle on the joints. Start with a short walk every day, even 10 minutes, and build up gradually. Every brisk walk, however short, counts towards the 150 minutes of weekly activity that WHO recommends for adults.
• Exercise at the right level. Our free workout videos come in three levels: Start (partly seated, no jumping), Build and Strong. You begin where you are and move up when you are ready.
• Good food. Our free eating plans are practical and flexible, without crash diets, with plenty of vegetables, fibre and protein, and fit your taste and daily life.
• Sleep and support. Good sleep, help with stress and people around you make healthy habits easier to keep. A free video meeting (in English) with our team can help you find the support that suits you.

You can sign up for free for the eating plans, the workout videos or a video meeting (in English). Read more about lifestyle treatment, the foundation of all obesity care.