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Medicines and surgery for obesity - Obesity

Your GP may prescribe medicine to treat obesity. Along with lifestyle changes, medicines can help you lose weight.

Before starting your new medicine, your GP will discuss:

  • your health history
  • your body mass index (BMI)
  • other complications of obesity, such as type 2 diabetes or high blood pressure
  • possible side effects

Medicines to treat obesity

Medicines to treat obesity target different parts of your body.

Brain and stomach

Some medicines to treat obesity target your brain and stomach. They work on the way your brain tells your body to eat.

They also work by slowing how food moves through your stomach. This can reduce appetite, and may cause weight loss.

Medicines used in this way include:

  • Liraglutide (also known as Victoza and Saxenda)
  • Semaglutide (also known as Ozempic and Wegovy)
  • Naltrexone or Bupropion (also known as Mysimba)


Some medicines prevent your bowel from absorbing fat.

Medicines that work this way include Orlistat (also called Xenical or Alli).

Talk to your GP if you think your medicine is not working, or if you are experiencing side effects.

Check if you can take obesity medicine

Tell your GP if you:

  • are pregnant or planning to get pregnant
  • are breastfeeding
  • have a family history of conditions such as high blood pressure, heart attack or stroke
  • are taking any other medicine

You may not be able to take some obesity medicines if you have another condition or are on other medicine.

Surgery to treat obesity

Weight loss surgery can be used to treat obesity. It's also known as bariatric surgery. 

Along with lifestyle changes, it can help you lose between 20% and 40% of your weight.

You may need to have bariatric surgery if:

  • you have serious health problems linked to your weight
  • lifestyle changes and medicine are not enough to treat obesity

When you can have bariatric surgery

Your GP may refer you for assessment and management in a bariatric surgery centre if you:

  • have a BMI of 40 or more
  • have a BMI between 35 and 40, and other conditions that could be improved with weight loss
  • have a BMI over 30 and a weight-related condition that cannot be managed with medicine
  • have made lifestyle changes and tried medicine but these have not improved your weight-related health problems enough
  • are safe to have anaesthetic and surgery
  • can commit to long-term follow-up

After bariatric surgery

The bariatric surgery team will focus on:

  • healthy eating
  • regular activity
  • healthy sleep
  • medicines
  • managing chronic pain, stress, and other health conditions

After surgery people can develop complications. These could include digestion problems, gallstones, or vitamin and mineral deficiencies.

After bariatric surgery you need to:

  • continue to have follow-up care and regular blood tests with your GP or the bariatric surgery team
  • take vitamins for the rest of your life as prescribed by your GP
  • continue with the lifestyle changes that you made before for your surgery
  • be aware that some people start to regain weight at about 12 to 18 months, or longer, after the surgery

Bariatric surgery can help people to lose weight. But if the causes of your weight gain are not also treated, you can put weight back on after surgery.

The bariatric surgery team will explore with you if there are any lifestyle or medical reasons for the weight gain and put a treatment plan in place.

Content supplied by the NHS and adapted for Ireland by the HSE

Page last reviewed: 9 August 2022
Next review due: 9 August 2025