Electrolytes: What they do, why you need them, and the best supplements

Apr 11

Electrolytes are substances that are often mentioned in connection with training and recovery, but the understanding of what they actually do in the body is far from obvious. It’s not about sports drinks with a neon green color - it’s about minerals that control everything from heart rhythm and muscle function to fluid balance and nerve signals. Without adequate levels of sodium, potassium, magnesium and calcium, neither performance nor basic body functions function optimally.

What are electrolytes and how do they work in the body

Electrolytes are minerals that, when dissolved in water, carry an electrical charge. That charge is what makes them so crucial: the body uses electrical signals to control muscles, nerves and organs. Sodium, potassium, magnesium, calcium, chloride and phosphate are all included in the group, but the first four are the ones that most often need attention in diet and exercise.

Sodium regulates the fluid balance and the pressure outside the cells. It helps the kidneys decide how much water to retain and how much to excrete. Sodium intake is directly linked to thirst and urine production – an interaction that the body adjusts minute by minute.

Potassium acts inside the cells and cooperates with sodium in the so-called sodium-potassium pump. Among other things, the pump drives muscle contractions and the regular beating of the heart. Low potassium levels are most clearly seen as muscle weakness, cramps and, in severe cases, heart rhythm disturbances.

Magnesium participates in over 300 enzymatic reactions and is needed for the cells to be able to produce energy in the form of ATP. It also regulates calcium channels in muscle cells, allowing muscles to relax after a contraction. Magnesium deficiency is more common than many people think – an estimated 10-30% of the population in Western countries suffer from suboptimal levels, according to data from recent years.

Calcium is often associated only with bones and teeth, but plays equally important roles in muscle contractions, blood coagulation and nerve signaling. Approximately 99% of the body’s calcium is stored in bones and teeth, but the remaining percentage that circulates in the blood is critical for minute operational functions.

Electrolyte deficiency – symptoms and risk groups

Electrolyte deficiency occurs when loss exceeds intake, either via sweat, urine, vomiting or inadequate diet. The symptom picture varies depending on which mineral is lacking and how pronounced the deficiency is.

Early signs of imbalance are often diffuse and easy to miss:

• Muscle cramps, especially in calves and thighs during or after exercise

• Fatigue and difficulty concentrating without a clear explanation

• Headache and dizziness, especially when changing position

• Palpitations or irregular heart rhythm

• Constipation or stomach cramps (common with magnesium deficiency)

• Increased thirst combined with frequent toilet visits

The risk groups for electrolyte deficiency are wider than many people expect. Endurance athletes lose between 1 and 2 liters of sweat per hour during intense exercise in the heat, and the sweat contains measurable amounts of sodium and potassium. Older people generally have lower dietary intake and poorer kidney function, which disturbs the mineral balance. People on a ketogenic or LCHF diet find themselves in a special situation: when glycogen stores are depleted and insulin levels drop, the kidneys excrete more sodium, which drags potassium and magnesium with it. It’s what many keto newbies call the “keto flu”—and it’s effectively an electrolyte deficiency.

Users of GLP-1 drugs (such as semaglutide) for weight loss constitute another group to watch out for. Decreased appetite leads to lower intake of minerals from the diet, and possible nausea and vomiting increase the losses. Regular monitoring of electrolyte status is recommended for this group – if you are using GLP-1 preparations, you should discuss mineral status with your attending physician.

Electrolytes and exercise – when supplements are actually needed

Exercise dramatically increases sweat production, but whether you need electrolyte supplements depends on the length of exercise, intensity and your individual circumstances. For sessions of less than 60 minutes in normal climates, water is enough for most people. The situation changes during longer sessions, high temperatures or when training in connection with a low-carbohydrate diet.

Sodium during long sessions

The sodium concentration in sweat varies greatly between individuals – from around 200 mg per liter to upwards of 1,800 mg per liter. This means that a “salt sweat” runner running a marathon in 15-20 degrees can lose 3,000-4,000 mg of sodium during the race. Drinking only water in that situation dilutes the remaining sodium in the blood, a condition called hyponatremia, which in severe cases can be life-threatening.

When exercising longer than 90 minutes, or shorter sessions in extreme heat, sodium supplementation (usually 500–1000 mg per hour) is often warranted. Potassium is added in lower doses, typically 100–300 mg per hour, depending on the amount of sweat.

Magnesium and recovery

Magnesium is the mineral that is most often forgotten in the context of training. Studies from 2018-2022 show that regular physical activity increases magnesium needs by an estimated 10-20% compared to sedentary individuals. Inadequate magnesium levels impair sleep quality, increase muscle soreness after exercise, and can contribute to chronic fatigue. Supplementing with 200–400 mg of magnesium per day—preferably in the evening—has been shown to improve sleep depth and reduce cramps in active individuals.

Electrolyte supplements in test – powders, tablets and sports drinks

The market for electrolyte supplements has grown significantly in recent years, ranging from simple salt tablets to advanced electrolyte powders with full mineral profiles. Understanding the differences will help you choose the right product for your purpose.

|Additional form|Benefits|Disadvantages|Best suited for|

|Electrolyte powder|Dosed flexibly, fast absorption, broad mineral profile|Requires mixing with water, costs more|Exercise, keto, daily use|

|Tablets/capsules|Easy to take, precise dosage|Slower absorption, difficult to adjust dose|Daily maintenance, travel|

|Sports drinks (liquid)|Smooth, often contains carbohydrates|High sugar content, low mineral concentration|Shorter training sessions with energy requirements|

|Breast tablets|Practical, good taste|Varying mineral content, often low sodium content|Light physical activity, children|

What to look for in an electrolyte powder

When comparing electrolyte powders – the format that dominates tests of electrolytes best in tests – the mineral composition is the most important criterion. A product worth investing in should include:

• Sodium in the range of 500–1,000 mg per serving

• Potassium 200–400 mg per portion

• Magnesium 50–200 mg per serving (often as malate, citrate or glycinate for better absorption)

• Calcium 50–200 mg per portion

Avoid products with unnecessary additives such as artificial colors, aspartame in high doses or ingredients you do not recognize. Also check if the product is certified for athletics use if you compete – doping contamination does occur in the industry, albeit rare.

A review of popular electrolyte powders on the Nordic market shows that the price differences are large: from around SEK 3 per portion for simpler products to SEK 15–25 for premium options. Price does not always correlate with quality – it is the mineral profile and the absence of unnecessary additives that determine the value.

Electrolytes in keto, LCHF and GLP-1 regimens

The ketogenic diet and LCHF create a unique electrolyte requirement that deviates from the standard recommendations. When carbohydrate intake drops below approximately 50 grams per day, glycogen stores are depleted within 24–72 hours. Each gram of glycogen binds approximately 3-4 grams of water, and when the glycogen is lost, the water goes with it – and takes electrolytes with it.

The need increases significantly already during the first weeks. Most people eating strict keto need to add 3,000-5,000 mg of sodium per day (significantly more than the 1,500-2,300 mg generally recommended), 2,000-3,500 mg of potassium, and 300-500 mg of magnesium. It is difficult to reach those levels through diet alone – electrolyte supplementation is for this group the rule rather than the exception.

Symptoms of electrolyte depletion during the keto transition include heart palpitations, leg cramps at night, dizziness upon standing up, and mental fog. Many feel these discomforts are inevitable, but in practice they are signs of a correctable mineral problem. Additions of sodium-rich broth, avocados, nuts and leafy greens combined with a well-formulated electrolyte powder will in most cases resolve the issues within 48-72 hours.

For people treated with GLP-1 drugs such as semaglutide or liraglutide, similar challenges apply, albeit for different reasons. The greatly reduced food intake – sometimes 30-50% fewer calories than before – automatically means lower mineral intake. Nausea and possible vomiting during the insertion phase worsen the picture further. Low-dose electrolyte supplements (a powder morning and night with water) can reduce fatigue and muscle weakness during the critical adjustment phase. Always discuss with your prescribing physician before starting supplements, especially if you have kidney or heart disease.

How to optimize your electrolyte intake in the long term

There is no one-size-fits-all dosage, but there is a structured way to find out what you need. Start with the diet: a varied diet with legumes, nuts, leafy vegetables, dairy products and meat covers the electrolyte needs of most physically active people in temperate climates.

Then add training volume and climate to the calculation. If you train more than four hours per week in the heat, or follow a restrictive diet, there is a good chance that the diet is not enough. A simple electrolyte powder on training days – and possibly a magnesium supplement every night – is a cost-effective and evidence-based way to close the gap.

Blood tests can provide further guidance. Standard panels measure sodium, potassium and calcium in the blood, but do not always cover magnesium or intracellular mineral levels. If you suspect a chronic deficiency, despite reasonable intake via diet and supplements, an extended mineral analysis may be worth discussing with a doctor.

The most important thing is not to wait for obvious symptoms. Suboptimal electrolyte levels—not clinical deficiency, but not optimal levels either—affect sleep quality, cognitive function, and performance in ways that are difficult to isolate without addressing. The right balance is an investment that is felt, but rarely all at once.

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