Electrolytes: The Ions That Keep Your Body Functioning

Electrolytes are minerals that dissolve in body fluids and carry an electrical charge — enabling nerve impulse transmission, muscle contraction (including the heart), fluid distribution across body compartments, acid-base balance, and cellular metabolism. The key electrolytes in clinical medicine are: sodium (Na⁺ — primary extracellular cation, determines fluid distribution), potassium (K⁺ — primary intracellular cation, critical for cardiac and skeletal muscle function), calcium (Ca²⁺ — essential for muscle contraction, nerve function, and bone mineral), magnesium (Mg²⁺ — cofactor for hundreds of enzymes), chloride (Cl⁻), bicarbonate (HCO₃⁻ — acid-base buffer), and phosphate.

Electrolyte imbalances are common and clinically significant. Hyponatraemia (low sodium) — the most common electrolyte abnormality in hospitalised patients — causes confusion, seizures, and, if severe, brainstem herniation. Hyperkalaemia (high potassium) — dangerous arrhythmia risk, particularly in kidney disease or ACE inhibitor use. Hypokalaemia (low potassium) — from diarrhoea, diuretics, or eating disorders — causes muscle weakness and cardiac arrhythmias. Hypercalcaemia — from malignancy or hyperparathyroidism — causes 'bones, groans, stones, and psychic moans'.

During Korea's hot, humid summers (jangma monsoon season and the peak heat of July–August), dehydration from sweat and inadequate fluid replacement is common, particularly among outdoor workers and athletes. Sweating depletes sodium along with water — in extreme heat stroke or exercise-associated hyponatraemia, replacement of fluid without sodium can dangerously dilute blood sodium. Oral rehydration solutions containing balanced electrolytes (not pure water alone) correct this optimally.