Electrolytes: when they matter

This is information, not a recommendation. We do not advise you to take anything. Under 18 or with an eating disorder, including a past one: this text is not aimed at you, and you will find places to turn to under When to get medical advice. During pregnancy or breastfeeding, with kidney disease or on medication, ask a doctor first.

What expert bodies say

Substance	Value for adults	Note
Sodium	1,500 mg a day according to the DGE,^[3] 2 g according to EFSA^[1]	The BfR advises against sodium in food supplements, except in special drinks^[2]
Potassium	4,000 mg a day according to the DGE,^[4] 3,500 mg according to EFSA^[5]	BfR proposal for food supplements: at most 500 mg per daily portion^[6]
Magnesium	350 mg for men, 300 mg for women^[7]	See Magnesium

What may be said in the EU

“Potassium contributes to normal muscle function” and “Potassium contributes to normal functioning of the nervous system”, only for foods that are at least a source of potassium.^[8]
“Magnesium contributes to electrolyte balance”, only for foods that are at least a source of magnesium.^[8]
“Carbohydrate-electrolyte solutions contribute to the maintenance of endurance performance during prolonged endurance exercise” and “Carbohydrate-electrolyte solutions enhance the absorption of water during physical exercise”.^[8]

The last two claims only apply to drinks with an exact recipe: 80 to 350 kcal per litre from carbohydrates, at least 75% of the energy from carbohydrates with a high glycaemic response, 460 to 1,150 mg of sodium per litre and an osmolality of 200 to 330 mOsm/kg water.^[8] So they do not apply to sugar-free powders. A claim on sodium and muscles is not authorised.^[9]

During training

The BfR considers sodium in special drinks useful to replace significant losses, for example through heavy sweating during intense exercise. It names 1,150 mg per litre, with a minimum of 460 mg.^[2] In a normal everyday training session this is rarely needed.

In long endurance events, drinking too much is also an issue. Blood sodium can then drop dangerously. An international consensus paper names sustained overdrinking as the main cause and considers drinking when thirsty the safest approach.^[10] More on everyday fluids is under Why the scales go up and down.

While losing weight

Drinks with an authorised claim deliberately contain carbohydrates, so calories.^[8] Count them if you count calories.
Salty food and drinking a lot can move the scale for a short time. That is water, not body fat.
There is no randomised trial of magnesium for cramps during exercise.^[11]
Fasting has its own rules, see Intermittent fasting.

When to ask a doctor

From normal food the risk for healthy people is low, because the body regulates potassium tightly. With products, case reports describe heart effects from 5,000 mg a day. With impaired kidney function, diabetes, heart disease and in older age, levels can rise dangerously.^[6]

Medication: ACE inhibitors, angiotensin receptor blockers and potassium-sparing diuretics reduce potassium excretion, so levels can get too high.^[12] The BfR passes on the advice to avoid potassium products in that case.^[6]
High blood pressure: A high sodium intake can raise the risk.^[3] Talk to your doctor before using salt tablets or electrolyte powders.
Diarrhoea, vomiting, severe weakness: These need medical attention rather than balancing things yourself.

The app does not replace medical advice.