Electrolytes are minerals that carry an electrical charge when dissolved in body fluids. They include sodium, potassium, calcium, chloride, magnesium, chloride and phosphate.   They are found in your blood, tissues and other body fluids and are essential for many of the body’s normal functions.

Electrolytes are important because they help:

• Balance the amount of water in your body
• Balance your body’s acid/base (pH) level
• Move nutrients into your cells
• Move waste products out of your cells
• Help your nerves, muscles, the heart, and the brain function normally
• Sodium is especially important for moving water into and out of cells

You get electrolytes from the foods you eat and the fluids you drink. In hot weather we lose both water and electrolytes through sweat. Some people drink plenty of water but eat less than usual, meaning they may not replace electrolytes at the same rate that they are being lost.

The levels of electrolytes in your body can become too low or, less commonly too high. Either can affect how the body functions.   Ever felt rubbish, fuzzy-headed and like it is hard to concentrate? This can happen when the amount of water in your body changes and your hydration balance is upset. Over the course of the day, the amount of fluid you take in should roughly balance the amount you lose. If something upsets this balance, you may have too little water (dehydration) or too much water (over-hydration).

In addition to warm weather and over or under hydration, some medicines, vomiting, diarrhoea, sweating, and liver or kidney problems can all upset the water and electrolyte balance within the body.

If you’re feeling mildly dehydrated after being out in the heat, move somewhere cool and have a drink. Water is usually the best choice for mild dehydration. If you’ve been sweating heavily, exercising for a prolonged period, or haven’t eaten, having a snack of a drink containing electrolytes (such as an oral rehydration solution or an isotonic sports drink) may help replace both fluids and salts. Fruit juice diluted with water can also help. Avoid excessive alcohol, which can worsen dehydration. Most people begin to feel better within 20-30 minutes once they have stated replacing fluids and, where needed, electrolytes.

Caution: Severe dehydration and prolonged exposure to heat can increase the risk of heat exhaustion and heat stroke. Heat stroke is a life-threatening medical emergency. If someone has a very high body temperature, becomes confused, loses consciousness or has a seizure, call 999 immediately and begin cooling them while waiting for an ambulance.

Older adults, babies and young children, pregnant women and people with long-term medical conditions are more vulnerable to dehydration and heat-related illness, so it’s especially important that they drink enough fluids during hot weather. Remember to check on elderly relatives, neighbours and anyone else who may be vulnerable. A quick phone call or visit to make sure they’re keeping cool and drinking enough fluids could make all the difference.

Top tip for those with children: If your small person is reluctant to drink in warm weather, an ice-lolly is essentially a drink on a stick and can be a great way to encourage extra fluid intake.

First published July 2021; Updated July 2026