Quick answer

Side effects depend on the amount and on who is drinking. The main risks are sodium above the 2,300 mg Daily Value day after day, potassium in people whose kidneys or medicines hold on to it, magnesium above 350 mg a day from supplements, and drinking far more fluid than you sweat.^1,2,3,4

Key facts

The average American eats about 3,400 mg of sodium a day before adding any drink mix.¹
Food magnesium does not count toward the 350 mg upper limit; supplements and medicines do.³
Many potassium supplements stop at 99 mg a serving, partly because of FDA rules on some potassium drugs.²
Drinks above about 1,000 mg of sodium per liter taste very salty.⁵

Too much sodium

Diets high in sodium are linked to a higher risk of high blood pressure, a major cause of stroke and heart disease, and blood pressure tends to rise with age.¹

Too much sodium can cause a serious buildup of fluid in people with heart failure, liver cirrhosis or kidney disease.⁶

These are effects of a high-sodium diet over time, not of a single drink. The concern with a daily high-sodium mix is that it adds to an intake that is already high: at 1,000 mg a serving, one a day takes the average American from about 3,400 mg to about 4,400 mg.¹

Drinks with more than about 1,000 mg of sodium per liter taste very salty and can be hard to drink.⁵

MedlinePlus says some people are more sensitive to salt and should eat less, including people over 50 and people with high blood pressure, diabetes or kidney problems.⁷

Too much potassium

Too much potassium from supplements or salt substitutes can raise blood potassium (hyperkalemia), especially with kidney disease or medicines that keep potassium in the body. It often causes no symptoms, but severe cases can cause dangerous heart rhythms.^2,8

Potassium supplements can cause minor stomach and gut side effects.²

Many supplement makers cap potassium at 99 mg a serving. FDA has ruled that some potassium chloride drug products above 99 mg are unsafe because of small-bowel injuries, and requires a warning on some potassium salts above that amount, though it has not ruled on supplements.²

Salt substitutes are the hidden source. They replace sodium chloride with potassium chloride and carry about 440 to 2,800 mg of potassium per teaspoon.²

Too much magnesium

High intakes of magnesium from supplements can cause diarrhea, nausea and abdominal cramping.³

Healthy kidneys pass extra magnesium from food, which is why food does not count toward the limit. Very large doses from laxatives or antacids, usually over 5,000 mg a day, have caused dangerously high magnesium levels, and the risk rises when the kidneys work poorly.⁹

Drinking more than you sweat

Drinking well beyond thirst during long exercise can dilute blood sodium, a condition called exercise-associated hyponatremia. Overdrinking is its most common cause, and severe cases are an emergency.^4,10

In the 2002 Boston Marathon, 13% of 488 runners tested at the finish had low blood sodium and 0.6% had critically low levels. Weight gain during the race, finishing times over 4 hours and very low or high body mass index were the risk factors; the type of drink was not.¹¹

Electrolyte drinks do not protect against this on their own. In the Boston study, how much runners drank mattered more than what they drank, and weight gain during the race was the strongest warning sign.¹¹

Older adults

Older adults can face both problems at once. Thirst can fade with age, while water pills and some blood pressure medicines change how the body handles potassium and sodium. Ask a doctor before starting a daily electrolyte product.^2,10,12

Medicines that change the picture

Potassium can build up with ACE inhibitors such as lisinopril, ARBs such as losartan, and spironolactone. Magnesium can keep tetracycline and quinolone antibiotics from being absorbed. Lithium levels shift with salt intake, and its label says not to change the amount of salt in your diet.^2,9,13

If you take any of these, ask your pharmacist before adding an electrolyte product, and bring its Supplement Facts panel.

Questions people ask

Is it safe to drink electrolytes every day?

It depends on the sodium and on how much you sweat. A daily mix with 1,000 mg of sodium adds to an average intake that is already about 3,400 mg, so the high-sodium kind fits training days better than rest days.¹

What are the signs of too many electrolytes?

Often there are none at first: high potassium frequently causes no symptoms. Diarrhea points to too much magnesium, and a very salty taste with more thirst points to a strong sodium mix. Palpitations, weakness, vomiting or trouble breathing while taking a potassium supplement need a doctor right away.^3,5,8

Can electrolytes cause diarrhea?

Magnesium can, when supplements push intake past 350 mg a day, and potassium supplements can cause minor stomach and gut upset.^2,3

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.