- People taking GLP-1 medicines such as Wegovy, Ozempic, Mounjaro and Saxenda may need to take extra care during hot weather.
- These treatments can reduce appetite and, for some people, may make it easier to forget to drink enough fluids.
- During a UK heatwave, dehydration can develop quickly, especially if someone is also experiencing nausea, vomiting or diarrhoea.
As temperatures rise across the UK, health professionals are warning that people taking GLP-1 medicines for weight loss or type 2 diabetes should be alert to the risk of dehydration.
GLP-1 based treatments can help people feel fuller, reduce hunger and support weight loss.
However, they can also cause side effects such as nausea, vomiting, constipation and diarrhoea, all of which can make dehydration more likely in hot weather.
The risk may be higher during a heatwave because people can lose more fluid through sweating, even when they are not exercising.
If someone is also eating less, drinking less or struggling to keep fluids down, symptoms can worsen quickly.
Why heat can be a problem on GLP-1 medicines
GLP-1 medicines work by affecting appetite and digestion. For many people, this means they feel less hungry and eat smaller portions.
But when appetite is lower, people may also drink less than usual.
Some may not notice they are thirsty until they are already mildly dehydrated.
This can be more of an issue during hot weather, when the body needs more fluid to stay cool.
People taking GLP-1 medicines should not rely on thirst alone during a heatwave. Instead, it may help to drink regularly throughout the day, especially during the morning and early afternoon when dehydration can creep up unnoticed.
Signs of dehydration to watch for
Common signs of dehydration include:
- Dark yellow urine
- Dizziness
- Tiredness
- Headaches
- Dry mouth
- Light-headedness
- Feeling unusually weak
Some people may also feel nauseous, shaky or faint, particularly if they have been standing outside, travelling on hot public transport or spending time in direct sun.
Anyone who is vomiting, has diarrhoea or cannot keep fluids down should speak to a pharmacist, GP or NHS 111 for advice.
Urgent help is needed if someone becomes confused, collapses, stops sweating despite feeling very hot or develops symptoms of heatstroke.
How to stay safer during a heatwave
People taking GLP-1 medicines can reduce their risk by planning ahead.
Keep water nearby, sip fluids regularly and consider setting reminders if you often forget to drink. If you are sweating heavily, an oral rehydration drink or electrolyte drink may be helpful.
Water-rich foods can also support hydration. Good options include cucumber, tomatoes, watermelon, berries, oranges, soups, yoghurt and salads.
It is also important not to skip meals completely just because you feel less hungry. Smaller, lighter meals may be easier to manage during hot weather, but the body still needs energy, protein and fluid.
Avoid the hottest part of the day
Try to avoid prolonged time outside during the hottest part of the day, usually between late morning and late afternoon.
If you need to go out, wear loose clothing, stay in the shade where possible and take water with you.
People travelling on buses, trains or the Tube should take extra care, as crowded transport can become very hot and uncomfortable.
Do not stop medication without advice
Anyone worried about side effects should not stop their GLP-1 medication without speaking to a healthcare professional first.
However, if vomiting, diarrhoea, dizziness or dehydration symptoms become significant, medical advice should be sought promptly.
This is particularly important for people taking GLP-1 medicines for type 2 diabetes, as dehydration and reduced food intake may affect blood glucose levels, especially if they are also taking insulin or other diabetes medication.
A heatwave reminder
GLP-1 medicines can be effective for weight management and diabetes care, but they are still prescription medicines that need proper monitoring.
During hot weather, the key advice is simple: drink regularly, eat enough, avoid overheating and get help early if symptoms worsen.
The heat can place extra strain on the body, and people taking GLP-1 medicines should take that risk seriously.
