Electrolyte Balance Guide: Sodium, Potassium, Magnesium, and More

Updated April 2026 · By the NutritionCalcs Team

Electrolytes are minerals that carry an electrical charge and regulate nerve function, muscle contraction, hydration, blood pH, and blood pressure. The major electrolytes — sodium, potassium, magnesium, calcium, chloride, and phosphate — must stay within tight ranges for normal cellular function. Imbalances cause symptoms ranging from muscle cramps and fatigue to cardiac arrhythmias and seizures. Athletes, people on low-carb diets, and anyone who sweats heavily need to pay particular attention to electrolyte intake.

The Major Electrolytes and Their Functions

Sodium is the primary extracellular electrolyte and the main regulator of fluid balance. It is lost in sweat at a rate of 500 to 2,000 mg per liter depending on the individual. Potassium is the primary intracellular electrolyte and is critical for muscle contraction and nerve signaling. The sodium-potassium pump that drives cellular function requires both in balanced proportions.

Magnesium is involved in over 300 enzymatic reactions including energy production, protein synthesis, and muscle and nerve function. It is the most commonly deficient electrolyte — an estimated 50 percent of Americans do not consume the recommended amount. Calcium supports bone health, muscle contraction, blood clotting, and nerve transmission. Chloride works with sodium to maintain fluid balance, and phosphate is essential for energy metabolism and bone structure.

• Sodium: fluid balance, nerve signaling — daily need: 1,500-2,300 mg
• Potassium: muscle contraction, heart rhythm — daily need: 2,600-3,400 mg
• Magnesium: energy production, muscle function — daily need: 310-420 mg
• Calcium: bone health, muscle contraction — daily need: 1,000-1,200 mg

Signs of Electrolyte Imbalance

Mild electrolyte imbalances cause subtle symptoms that are easy to dismiss: fatigue, muscle cramps, headaches, dizziness, brain fog, and irregular heartbeat. These symptoms are non-specific and overlap with dehydration, poor sleep, and stress, which is why electrolyte deficiency is frequently undiagnosed. Athletes who cramp during training despite adequate hydration often have a sodium or magnesium deficit rather than a water deficit.

Severe imbalances are medical emergencies. Hyponatremia (low sodium) from excessive water intake without sodium replacement causes confusion, seizures, and brain swelling. Hyperkalemia (high potassium) from kidney disease or excessive supplementation causes dangerous cardiac arrhythmias. Severe hypomagnesemia causes tremors, seizures, and cardiac arrest. These severe imbalances typically occur in clinical settings or extreme athletic events, not daily life.

Electrolytes for Athletes

Sweat losses during exercise require intentional electrolyte replacement. A 2-hour training session in warm conditions can lose 1 to 2.5 liters of sweat, containing 500 to 2,000 mg of sodium, 100 to 400 mg of potassium, and smaller amounts of magnesium and calcium. Plain water replaces the fluid but not the electrolytes, which is why athletes who drink only water during prolonged exercise risk hyponatremia.

For exercise lasting under 60 minutes, water alone is usually sufficient. For exercise lasting 60 to 120 minutes, a sports drink or electrolyte supplement providing 300 to 600 mg of sodium per liter is recommended. For exercise exceeding 2 hours, especially in heat, target 600 to 1,000 mg of sodium per liter along with potassium and magnesium. Individual sweat rates and sodium concentration vary widely — some athletes lose three times more sodium per liter than others.

Food Sources vs Supplements

Most people can meet electrolyte needs through food if they eat a varied, whole-food diet. Potassium-rich foods include bananas, potatoes, spinach, avocados, and beans. Magnesium-rich foods include nuts, seeds, dark chocolate, and leafy greens. Sodium is abundant in processed foods but may need to be intentionally added when eating a whole-food diet, especially on low-carb diets that increase sodium excretion.

Electrolyte supplements are useful for athletes, people on ketogenic diets (which increase electrolyte excretion), and anyone with conditions that increase losses. Look for supplements providing sodium, potassium, and magnesium without excessive sugar. Many commercial sports drinks contain more sugar than electrolytes — read labels. Electrolyte powders or tablets mixed into water provide controlled electrolyte dosing without unnecessary calories.

Special Populations and Considerations

People on ketogenic and very-low-carb diets excrete significantly more electrolytes due to lower insulin levels. Sodium needs may increase to 3,000 to 5,000 mg per day, potassium to 3,000 to 4,700 mg, and magnesium to 300 to 400 mg. The "keto flu" that many people experience during the first week of carb restriction is primarily electrolyte depletion, not carbohydrate withdrawal.

Older adults are at higher risk of electrolyte imbalance due to decreased kidney function, medications (diuretics are a common cause of potassium depletion), and reduced dietary intake. People with heart failure, kidney disease, or diabetes should work with their healthcare provider before significantly increasing electrolyte intake, as their conditions may require specific electrolyte restrictions.