Educational guide
GLP-1, explained.
A balanced, educational guide to GLP-1: the natural hormone, the medicines that act like it, how they are used in weight management, and their risks.
What is GLP-1?
Glucagon-like peptide-1 (GLP-1) is a hormone your gut releases after you eat. It helps the body release insulin when blood sugar rises, slows how quickly the stomach empties, and acts on areas of the brain involved in appetite and fullness.
What are GLP-1 medicines?
GLP-1 receptor agonists are medicines that act like the natural hormone, but for longer. They were first developed to treat type 2 diabetes. Some are now licensed in the UK for weight management in adults, alongside a reduced-calorie diet and increased physical activity. A related group, dual GIP and GLP-1 receptor agonists, act on two hormone pathways.
These are prescription-only medicines. They must be prescribed by a qualified prescriber after an assessment, and supplied by a registered pharmacy.
How they work in weight management
By slowing stomach emptying and acting on appetite signals, these medicines can help people feel full sooner and for longer, which can reduce how much they eat. They don’t replace changes to diet and activity; licensed use is always alongside them.
Common side effects
The most commonly reported side effects affect the digestive system, particularly when starting or increasing the dose:
- feeling or being sick
- diarrhoea or constipation
- stomach pain, bloating or indigestion
- headache, tiredness or dizziness
Serious side effects
Less commonly, these medicines can cause serious problems. Get urgent medical help for severe, persistent stomach pain (which can be a sign of pancreatitis), signs of gallbladder problems, severe dehydration, or signs of a serious allergic reaction. People who also take some diabetes medicines may be at risk of low blood sugar.
Tell anyone treating you — including before surgery or a procedure under sedation — that you take one of these medicines.
Who should not use them
They aren’t suitable for everyone. They are not used during pregnancy or breastfeeding, and effective contraception is advised for people who could become pregnant. Some medical histories mean they would not be safe. A prescriber decides individually.
After stopping
Studies show that many people regain some weight after stopping treatment. That’s one reason ongoing lifestyle support matters.
Reporting side effects
You can report suspected side effects of any medicine to the MHRA through the Yellow Card scheme.
Frequently asked questions
Is GLP-1 the same as a weight loss medicine?
No. GLP-1 is a natural hormone. GLP-1 receptor agonists are medicines that act like it; some are licensed for weight management and others for type 2 diabetes.
Can I buy GLP-1 medicines without a prescription?
No. In the UK they are prescription-only medicines. They must be prescribed by a qualified prescriber and supplied by a registered pharmacy. The MHRA warns that products sold without a prescription may be unlicensed, fake or unsafe.
Do GLP-1 medicines work on their own?
They are licensed for use alongside a reduced-calorie diet and increased physical activity, not instead of them.
Sources and further reading
This page is for general education only. It isn’t medical advice, it doesn’t recommend any treatment, and it doesn’t replace a conversation with a qualified healthcare professional about your own circumstances. If you need urgent medical help, call 999 or NHS 111.