As Britain braces for a scorching bank holiday weekend with temperatures expected to hit a record-breaking 33C, experts are urging those taking weight loss injections to be vigilant about a key symptom: dehydration. The surge in popularity of GLP-1 receptor agonists, including semaglutide, has transformed weight management, but the combination of hot weather and medication side effects could pose serious health risks.
Why Weight Loss Jabs Increase Dehydration Risk
GP and medical advisor Dr Suzanne Wylie from IQdoctor explained that these injections can heighten the risk of dehydration during a heatwave. "Weight-loss injections containing GLP-1 receptor agonists, such as semaglutide, have transformed obesity treatment and weight management, but they can increase the risk of dehydration, especially during periods of warmer weather," she said. "This is largely because some of the most common side effects include nausea, vomiting and diarrhoea, all of which can lead to significant fluid loss."
These medications also slow gastric emptying, helping individuals feel fuller for longer. However, this can unintentionally reduce overall food and fluid intake. "Staying hydrated is one of the easiest and most important ways for people using weight-loss medications to protect their health," Dr Wylie added.
Recognising Dehydration Symptoms
Our bodies naturally lose more fluids through sweating in hot weather, and these losses must be replenished. If someone is already experiencing medication side effects that reduce fluid intake or increase fluid loss, they may be more vulnerable to dehydration-related illnesses such as heat exhaustion and, in more serious cases, heatstroke.
Dehydration symptoms include headaches, fatigue, dizziness, dry mouth, and darker urine. More severe dehydration may cause confusion, weakness, muscle cramps, or feeling faint. While drinking more fluids helps, Dr Wylie emphasised that waiting until thirst strikes is too late. "Many people wait until they feel thirsty before drinking water, but thirst often occurs after the body has already started becoming dehydrated. Instead, it is important to drink regularly throughout the day, even if you don't feel particularly thirsty."
Practical Tips for Staying Hydrated
Adults should aim for around eight glasses of fluid daily—approximately 1.5 to 2 litres—and increase this during a heatwave. Dr Wylie suggests:
- Carrying a water bottle and sipping regularly throughout the day
- Setting reminders to drink fluids
- Eating water-rich foods such as watermelon, cucumber, and oranges
- Flavouring water with sugar-free squash if plain water becomes unappealing
- Limiting excessive sugary drinks and alcohol
Lesser-Known Concern: Gallstones
According to Dr Wylie, there is a lesser-known concern associated with dehydration. "Gallstones are a recognised but relatively uncommon side effect linked to rapid weight loss and some weight-loss medications. Dehydration may further increase this risk because it can reduce bile flow and cause bile to become more concentrated within the gallbladder."
If anyone starts to feel unwell with persistent dizziness, severe fatigue, worsening nausea, or symptoms of dehydration, they should seek medical advice promptly.
