What are electrolytes?

What electrolytes do

The National Library of Medicine’s MedlinePlus describes the jobs electrolytes share: balancing the water in your body, keeping your blood’s acid level steady, moving nutrients into cells and waste out of them, and supporting nerve and muscle function.

You don’t need to memorize the chemistry. For exercise, one fact matters: of everything you lose in sweat, sodium is lost in the largest amounts and has the biggest effect on your body’s fluid balance ^[1]. That’s why sports drinks are built around it.

The electrolytes on a drink label

Sodium

The headline electrolyte. Baker’s 2017 review of sweat research says sodium is lost in the greatest amounts and has the biggest effect on body fluid balance ^[1]. Whole-body sweat usually carries 230 to 1,610 mg/L of sodium ^[1]. In a drink, sodium also helps trigger thirst and helps you retain the fluid you drink ^[6].

Is salt an electrolyte? Table salt is sodium chloride. Dissolved in water, it splits into two electrolytes: sodium and chloride. So “salt” and “electrolytes” overlap, but they aren’t the same thing.

Chloride

Sodium’s usual partner. Most of the sodium in food and drinks arrives as sodium chloride, so chloride comes along with it. Many US labels don’t list chloride because the Nutrition Facts panel doesn’t require it, which is why our database shows it as “not on label” for many drinks.

Potassium

Found in most sports drinks in smaller amounts than sodium. Sweat contains far less potassium than sodium ^[1], so drinks built to match sweat losses carry more sodium than potassium. For reference, the WHO oral rehydration formula includes 20 mmol/L of potassium ^[4].

Magnesium and calcium

Both appear on some electrolyte labels, usually in small amounts. You lose them in sweat in much smaller quantities than sodium ^[1]. Some brands market magnesium heavily. Their presence on a label doesn’t tell you the drink will do anything specific for you.

Bicarbonate and phosphate

These matter inside the body, but they rarely show up on sports drink labels as separate lines. You may still see citrate or phosphate salts in ingredient lists.

Reading electrolytes on a label

Labels list electrolytes in milligrams per serving. Research papers usually use millimoles (mmol), which count particles instead of weight. To convert:

• sodium: multiply mmol by 22.99 mg/mmol
• potassium: multiply mmol by 39.1 mg/mmol

Serving sizes vary, so compare drinks on a common basis. Our product pages show every electrolyte per serving, per 12 fl oz and per liter. Here’s how three different approaches look per serving:

• Nuun Sport (one tablet): 300 mg sodium, 150 mg potassium, 25 mg magnesium
• LMNT (one stick): 1,000 mg sodium, 200 mg potassium, 60 mg magnesium
• Gatorade Thirst Quencher (one labeled serving): 270 mg sodium, 80 mg potassium

The spread is wide. Our guide to sodium in sports drinks puts every drink side by side, and the drinks database lets you filter and sort by any electrolyte.

“More electrolytes” isn’t automatically better

Marketing often treats electrolyte totals as a score. They aren’t. What matters is whether the drink roughly matches what you lose, and that depends on your sweat rate and how salty your sweat is. Both vary a lot from person to person ^[2].

Someone doing a 40-minute gym session in air conditioning loses a small amount of sodium that normal meals replace ^[6]. Someone running a hot marathon may lose a lot more. The same drink can be overkill for one and not enough for the other. Our guide on whether you need electrolytes walks through the common situations, and the hydration calculator turns your session into a sodium target.

Where else electrolytes come from

Food is the other source. After exercise, the ACSM position stand says normal meals and snacks with enough sodium, plus water, restore hydration when time allows ^[6]. Drinks matter most during long sessions, when eating isn’t practical.

Electrolyte imbalance

MedlinePlus lists several causes of electrolyte imbalance, including heavy sweating, severe vomiting or diarrhea, some medicines, organ disease, and drinking too much water. That last one matters for athletes. Exercise-associated hyponatremia, a drop in blood sodium during exercise, is mainly caused by drinking more fluid than you lose, and the advice is to drink to thirst ^[5].

If you think you have an electrolyte imbalance, or you have a heart, kidney or blood pressure condition, talk to a doctor rather than self-treating with electrolyte products.