About Sodium
Blood sodium is the primary electrolyte controlling fluid distribution, blood pressure, and nerve-impulse transmission — and abnormal levels rarely reflect how much salt you eat. They almost always indicate a problem with how the kidneys and hormones (ADH, aldosterone) regulate water balance. Both hyponatremia (low sodium) and hypernatremia (high sodium) range from mildly symptomatic to life-threatening depending on the degree and speed of change.