Should you be taking electrolyte supplements?
I have completed two nutrition workshops in the past week, both of which we got on to the topic of electrolytes. There were A LOT of questions, and unfortunately not much time to dig into the science and recommendations in depth. So here we go…
What is an electrolyte?
Electrolytes are minerals that carry an electrical charge when dissolved in body fluids, for example - sodium, potassium, chloride, calcium, magnesium and phosphate. They regulate fluid balance, nerve impulses, muscle contraction and blood pressure.
Sodium is the electrolyte which we lose most of in sweat, and is one of the main determinants of our fluid balance. It also helps drive thirst, so we can use it to our advantage to encourage adequate hydration. When we think about electrolytes and hydration, sodium is the main electrolyte we need to be considering.
Do you need electrolytes every day?
Most people will get electrolytes through their diet and DO NOT NEED TO TAKE ELECTROLYTE SUPPLEMENTS DAILY.
For example, sodium and chloride are the components of salt. According to the National Diet and Nutrition Survey, which used measurement of 24-hour urine collections to identify salt intake in the diet, the average salt intake for adults is 8.4 grams per day, which is higher than the maximum of 6 grams per day recommended.
Your kidneys and sweat glands will also adjust the sodium lost in sweat and urine depending on your intakes, so if you eat more sodium you will excrete more, if you eat less you will conserve more.
We also get other electrolytes from food, such as calcium and phosphate from milk and cheese, potassium from bananas and potatoes, magnesium from leafy greens and seeds.
What about around exercise?
When you exercise, you will lose sweat and therefore lose electrolytes (mainly sodium). You also want to be going into exercise hydrated, and make sure you rehydrate after exercise, and sodium may support this process.
Forms of sodium for exercise
Salt - around 1 level teaspoon contains 2300-2400mg sodium. You can use these figures to work out how much salt to add to fluids as per the recommendations below.
Pre-made sports drinks - these often have added electrolytes (including sodium) in them, but are sometimes in lower quantities so may not be appropriate if you need specific, higher sodium quantities during exercise over 4 hours (see during exercise section below).
Electrolyte supplements - these can vary from 300-1000mg sodium per tablet, and your needs will differ depending on the exercise. They are available in effervescent / soluble forms or tablets that you swallow. These could be helpful if you are wanting to achieve specific sodium intakes, or if you struggle with the taste of fluids with salt in, the swallowable tablets may be a good alternative (as long as you are drinking adequate fluids alongside). However, if you are not needing aggressive targeted electrolyte supplementation, these are the more expensive option and salt as above may be sufficient to encourage fluid intake.
Before exercise
Adding a little bit of sodium to fluid (around 100-125mg sodium per 100mL, or just under ½ level teaspoon in 1 litre of fluid, in a drink itself or 275-420mg sodium per 100mL of your desired fluid intake when having capsules or salty food) can increase thirst, which can then support adequate pre-exercise hydration. If you are someone who struggles to drink before exercise, this could be a strategy you could use to increase thirst and fluid intake.
If you are good at drinking pre-exercise, tend to go in hydrated, and are training or competing in an event in colder climates where you aren’t sweating lots, this advice may not apply to you.
Pre-loading electrolytes for multiple days before an event is not recommended as your kidneys will just excrete most of the extra. There may be a place for some individuals to pre-load sodium for the 4 hours before an event, but this is typically only required if you are competing in endurance events in warm or hot environments, sweating a lot and/or unable to replace your losses during the event. If this is the case, I would recommend reaching out to a registered sports nutrition professional (like me) for more tailored advice.
During exercise
In theory, adding small amounts of sodium to fluids (up to 1000-1200mg per 1 litre, or ~1/2 or less of a level teaspoon salt, per 1 litre) may increase thirst drive and encourage fluid intake during exercise, but the evidence is mixed.
What is clear is that sodium per se does not seem to directly improve performance. BUT it may help performance indirectly if it results in you drinking more fluid and staying hydrated. This reframes sodium as something that supports your fluid strategy rather than a standalone intervention.
When is low sodium a potential risk during exercise?
Blood sodium is at risk of falling if you have all of these things:
Exercise lasting longer than four hours
You are losing sweat at a rate less than 1.8 litres per hour
You are replacing more than 70% of your fluid losses (but less than 100%) with fluid
Typically this is athletes competing in endurance/ ultra-endurance events, or long team sport training sessions in the heat. If you have said yes to all three of the above, sweat sodium testing and individualised advice may be worthwhile, guided by a sports nutrition professional.
Also, if you are losing more than 1.8 litres per hour of sweat, it will likely be impractical to replace >70% of this with fluid but I would still recommend you reach out to a registered sports nutrition professional for tailored advice. You will be at a higher risk of dehydration at the above sweat rates.
In most other cases, seasoning fluid to taste (up to 1000-1200mg per 1 litre, or ~1/2 or less of a level teaspoon salt, per 1 litre) may help thirst and encourage hydration, but aggressive targeted replacement of sodium/ electrolytes is typically not needed.
After exercise
Adding sodium to a rehydration drink (275-420mg or potentially less sodium per 100mL of fluid consumed) may help you retain fluid, BUT the effect is clearest when you are drinking water on its own. Having a drink alongside a meal, or choosing a recovery drink like milk will support rehydration and adding extra sodium to fluids is likely not needed.
Main Takeaways
Daily electrolyte supplementation is not necessary for most people.
If you struggle to drink before exercise, sodium can help increase thirst and encourage fluid intake. If you tend to go into exercise hydrated, and you are not doing endurance/ ultra-endurance or prolonged team training sessions in the heat, this may not apply to you.
If you are doing exercise for longer than 4 hours, are losing less then 1.8 litres per hour in fluid, and are replacing more than 70% of fluids (but less than 100%) lost, you may be at a higher risk of developing low blood sodium. In this case contact a registered sports nutrition professional for tailored advice.
If you do not meet the above criteria, adding a small amount of sodium to fluids may help palatability and encourage fluid intake (although the evidence is mixed), but aggressive targeted electrolyte replacement is probably not necessary.
After exercise, if you are just having plain water you may want to add some sodium to help fluid retention, but if you are having fluids alongside foods or milk, you likely do not need this.
Please note this is general guidance only. Please consult with your GP or medical practitioner for your personal needs, especially if you have medical conditions which may have different requirements such as POTS.
References and Resources:
Public Health England. National Diet and Nutrition Survey: Assessment of salt intake from urinary sodium in adults (aged 19 to 64 years) in England, 2018/19. Available at: https://assets.publishing.service.gov.uk/media/5e7cd9cdd3bf7f133ed1b6a1/Report_England_Sodium_Survey_2018-to-2019__3_.pdf
McCubbin AJ. Sodium intake for athletes before, during and after exercise: review and recommendations. Performance Nutrition. 2025;1:11. Available at: https://doi.org/10.1186/s44410-025-00011-9
This is also a very helpful article - https://www.mysportscience.com/post/the-role-of-sodium-during-exercise