Guidance

GLP-1 medicines for weight loss and diabetes: what you need to know

Published 5 June 2025

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GLP-1 medicines and what they are used for

Glucagon-like peptide-1 receptor agonists (GLP-1s or GLP-1RAs) are medicines that help people feel fuller by mimicking a natural hormone released after eating. Some newer medicines, like Mounjaro, also act on a second hormone involved in appetite and blood sugar control. You may see them referred to in the media as “weight loss injections” or “skinny jabs” but not all of these medicines are authorised for weight loss.

In the UK, there are three licensed GLP-1 medicines – semaglutide (sold under the brand names Wegovy, Ozempic and Rybelsus), tirzepatide (Mounjaro) and liraglutide (sold under various brand names). “Licensed” means they have been assessed carefully by the UK medicines regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), and approved as safe and effective for certain uses, outlined in the table below.

The MHRA has not assessed the safety and effectiveness of these medicines when used outside of their licensed use, for example when used for weight loss in people who are not obese or overweight.

GLP-1s are medicines licensed to treat specific medical disorders and should not be used if you are not overweight or diabetic or want to lose weight for aesthetic or cosmetic purposes.

Licensed to treat diabetes alongside a reduced calorie diet and exercise Licensed for weight loss/management alongside a reduced calorie diet and exercise in people with obesity, or people who are overweight with weight-related health problems
Semaglutide
(Wegovy)		 Yes Yes*
Semaglutide
(Ozempic and Rybelsus)		 Yes No
Tirzepatide†
(Mounjaro)		 Yes Yes
Liraglutide
(all brands)		 This is brand specific, please check the product information leaflet This is brand specific, please check the product information leaflet

*Wegovy can also be used to reduce the risk of cardiovascular events (heart attack and stroke) in overweight and obese individuals.

†Tirzepatide (Mounjaro) is a dual receptor agonist for GLP-1 and glucose-dependent insulinotropic polypeptide (GIP).

Where to find GLP-1 medicines

All GLP-1 medicines are prescription only medicines, which means they can only be prescribed by a healthcare professional.

Some GLP-1 medicines are available on the NHS. Availability may vary depending on your location and whether treatment is for diabetes or for weight loss.

GLP-1 medicines can also be purchased privately. If you want to get a GLP-1 medicine privately, a consultation with a healthcare professional must happen before the prescription can be issued, so that the prescriber can carry out proper checks and make sure you are aware of the benefits and risks of taking the medicine.

GLP-1 medicines should not be bought from unregulated sellers such as beauty salons or via social media, or from anywhere without a prior consultation with a healthcare professional. We have had reports of people experiencing severe side effects from fake GLP-1 medicines.

Legitimate GLP-1 medicines are provided in pre-filled injection pens. Products supplied as a powder in vials which must be mixed with a liquid prior to injection are not authorised and pose significant health risks. There have also been reports of counterfeit pre-filled pens that closely mimic the appearance of the licensed products. These may look genuine but can also be dangerous. Not only does buying from unregulated sellers expose people wanting to lose weight to serious health risks – it is also against the law to sell these medicines in this way.

The only way to guarantee you receive a genuine GLP-1 medicine is to obtain it from a legitimate pharmacy, including those trading online, with a prescription issued by a healthcare professional.

For pharmacies based in Great Britain you can check on the General Pharmaceutical Council’s (GPhC) website that it is properly registered. For pharmacies based in Northern Ireland please refer to the Pharmaceutical Society of Northern Ireland’s (PSNI) website.

For further information about use of online pharmacies, please also refer to the General Pharmaceutical Council’s guide on how to keep safe when getting medicines or treatment online.

You can also visit our #FakeMeds website for tools and resources to help you purchase medicines or medical devices safely online.

Risks of taking GLP-1 medicines

Like all medicines, GLP-1 medicines can cause side effects. Some of the most common side effects are gastrointestinal effects such as nausea, vomiting, and diarrhoea. These side effects were observed in clinical trials for these products and make up the majority of the Yellow Card reports the MHRA receives for these products. Most side effects are mild to moderate in severity or short in duration. However, some (such as nausea, vomiting and diarrhoea) sometimes lead to more serious complications such as severe dehydration, resulting in the need to go to hospital.

Although infrequent, inflammation of the pancreas (known as acute pancreatitis) has been reported with GLP-1 medicines. This can be serious. The main symptom of this is severe pain in the stomach that radiates to the back and does not go away. Anyone who experiences this should seek immediate medical help.

A full list of the known side effects can be found in the product information for the individual medicines.

GLP-1 medicines, contraception and pregnancy

All individuals of child-bearing potential (who are able to become pregnant) using GLP-1 medications should take steps to ensure they do not become pregnant.  

GLP-1 medicines should not be taken during pregnancy or just before trying to get pregnant. This is because there is not enough safety data to know whether taking a GLP-1 medicine can cause harm to the baby. In some animal studies, GLP-1 medicines were found to be harmful to the unborn foetus, although more information is needed to see whether or not this same effect would be seen in humans. If you are using a GLP-1 medicine and think you might be pregnant, speak to a healthcare professional straight away.

As a precautionary measure, you should use contraception while taking GLP-1 medicines and for a defined “wash-out” period after (the length of time the medicine should be stopped before trying to get pregnant).

How many months should GLP-1 be stopped before pregnancy?
Semaglutide
(Wegovy, Ozempic and Rybelsus)		 At least 2 months
Tirzepatide
(Mounjaro)		 At least 1 month
Liraglutide
(All brands)		 0 months*

*These medicines leave your body much quicker than the other GLP-1 medicines, which means they should be stopped just before trying to become pregnant.

If you are using Mounjaro (tirzepatide) and you are taking an oral contraceptive (the pill) you should use a non-oral form of contraception for four weeks after starting GLP-1 medicines, and for four weeks after any increase in dose. This can be a barrier form of contraception (e.g. condom) alongside your pill, or switching to a non-oral contraceptive like the coil or implant. This is because the medicine may reduce the effectiveness of oral contraceptives in those who are overweight or obese. 

For further information on GLP-1s and contraception use, please see guidance from The Faculty of Sexual and Reproductive Health (FSRH). If you have any concerns, speak to a healthcare professional.

GLP-1 medicines and breastfeeding

GLP-1 medicines should not be taken by people who are breastfeeding. This is because there is not enough safety data to know whether taking a GLP-1 medicine can cause harm to the baby. If you have any concerns, speak to a healthcare professional.

GLP-1 medicines and depression or suicidal thoughts

Following a comprehensive safety review, the MHRA concluded that the available data does not support a causal association between GLP-1s and depression, suicidal ideation and suicide.

The MHRA will continue to closely monitor the risk of severe psychiatric reactions associated with these medicines and will assess new data as it becomes available.

Using GLP-1 medicines around the time of a surgery or an operation

If you are taking a GLP-1 medicine, make sure you inform your healthcare team including the anaesthetist about this prior to your surgical procedure.

This medicine slows the emptying of your stomach, increasing the risk that stomach contents (e.g. food and drink) could enter into your airways and lungs during surgery or procedures whilst you are under general anaesthesia or deep sedation. This means that a modification to the pre-procedure instruction and anaesthetic technique may be required.

Continue to take your prescribed medicine(s) as usual and do not stop your treatment without first discussing this with your doctor.

Further information to be aware of

We keep all medicines under continual review. Through this monitoring, we may learn new things about these medicines, especially as GLP-1 medicines are relatively new.

The MHRA communicates any new information on GLP-1s as quickly as possible where it is appropriate to do so. A list of our most recent, relevant communications can be found below.

Anyone who suspects that they’ve had an adverse reaction to a GLP-1 medicine, or who suspects it is not a genuine product, should report it to our Yellow Card scheme.

Summary: What do those taking or planning to take these medicines need to remember

  • You should only take GLP-1 medicines if they have been prescribed to you by a healthcare professional
  • Always have a conversation with your prescriber about the benefits and risks of GLP-1 medicines before you start taking them
  • Do not take GLP-1 medicines if you are pregnant, trying to get pregnant or breastfeeding. If you get pregnant while using them, talk to a healthcare professional straight away
  • If you are prescribed Mounjaro (tirzepatide), and you are using an oral contraceptive (the pill), use a non-oral form (such as condoms, the coil, or implant) of contraception in addition to your pill for four weeks after starting GLP-1 medicines, and for four weeks after any increase in dose
  • Understand the potential side effects and have a conversation with a healthcare professional if you are concerned
  • Tell your doctor you take a GLP-1 medicine if you are about to have surgery
  • Report any adverse reactions to the Yellow Card scheme
  • After taking the recommended four doses in your syringe, any medicine left in the syringe should not be extracted and should be disposed of in the bin
  • Use of these medicines is not a quick fix to lose weight and the MHRA has not assessed the safety and effectiveness of these medicines when used by people who do not meet the medical requirements
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