Medicines and weight gain

Also called medicine-related weight gain

Key points about medicines and weight gain

  • Some medicines can cause weight gain as a side effect for some people. The amount of weight gained depends on the individual and type of medicine.
  • If you're underweight or an average weight, gaining a few kilos might not matter to you. But if you're already overweight, gaining more weight can be a concern.
  • Medicines can cause weight gain in several ways.
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Medicines can cause weight gain in several ways. They can:

  • stimulate your appetite, making you feel hungry, eat larger portions and/or eat more often
  • affect the way your body stores fat
  • slow your metabolism, which causes your body to burn calories at a slower rate
  • make you retain fluid
  • affect your ability to exercise, such as by causing shortness of breath or making you feel too tired to exercise.

With some medicines, it isn't exactly clear what triggers the weight gain.

The following is a list of medicines known to cause weight gain for some people. It's important to note that not all people gain weight with these medicines.

If you're taking a medicine and are worried about weight gain, do not stop taking your medicine suddenly. Discuss this with your healthcare provider.

There might be a different medicine that you can take that has less of an effect on your weight. Stopping or changing medicines should be balanced against the risks of gaining weight and related health effects.

Medicines that are known to cause weight gain for some people
  • Medicines for diabetes such as insulin and sulfonylureas.
  • Antipsychotics such as haloperidol, clozapine, lithium, olanzapine.
  • Antidepressants such as amitriptyline, paroxetine, sertraline.
  • Medicines for epilepsy such as sodium valproate, carbamazepine.
  • Beta-blockers such as metoprolol, atenolol and propranolol.
  • Steroid medicines such as prednisone, dexamethasone.
  • Oral contraceptives (birth control pills).
Note: Not all medicines of these types cause weight gain, eg, metformin (a drug used for diabetes) and topiramate (a drug used for seizures and migraines) might make you lose weight.

Working out whether your weight gain is caused by your medicine isn't always easy. Your healthcare provider will look at your medicine list to see whether you're taking any that can cause weight gain. If you started gaining weight when you began 1 of these medicines, then it could be a cause.

To work out whether a medicine is responsible for your weight gain, your healthcare provider will note your change in weight compared with records from your past appointments. They may ask you about changes in your eating or exercise habits. They may also do a physical exam to make sure your weight gain isn’t caused by something else.

Talk to your healthcare provider

If you're worried about putting on weight, don't stop taking your medicine suddenly. Instead, discuss this with your healthcare provider. Some medicines need to be stopped gradually, as stopping suddenly can make you feel very unwell.

Sometimes a more suitable medicine can be found. They may discuss various weight loss options that best suit your needs. Read more about options for weight loss. 


Ask for a referral to a dietitian or a nutritionist

They can give you guidance on healthy eating plans and practical advice on food choices.

Common questions to ask about the medicines you are taking
Medicines and side effects
Healthy eating basics
Weight loss topics

Brochures

(external link)Medicines and side effects(external link) Healthify He Puna Waiora, NZ, 2024
(external link)5 questions to ask about your medications(external link) Health Quality and Safety Commission, NZ, 2019 English(external link), te reo Māori(external link)


Apps

Healthy eating/nutrition apps
Fitness and weight loss apps


References

  1. Domecq JP, Prutsky G, Leppin A, et al. Clinical review – drugs commonly associated with weight change: a systematic review and meta-analysis(external link) J Clin Endocrinol Metab. 2015 Feb;100(2):363–70 
  2. When your weight gain is caused by medicine(external link) University of Rochester, UK 
  3. Antidepressants and weight gain – what causes it?(external link) Mayo Clinic, US, 2024 

Brochures

Medicines and side effects
Healthify He Puna Waiora, NZ, 2024

5 questions to ask about your medications

5 questions to ask about your medications

Health Quality and Safety Commission, NZ, 2019 English, te reo Māori

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Stephanie Yee, Pharmacist, Auckland

Last reviewed:

Read more at: https://healthify.nz/medicines-a-z/m/medicines-and-weight-gain/
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