The Great Dilution: How Your Blood Chemistry Changes with Too Much Water

Your blood is a complex and carefully balanced solution of cells, proteins, and electrolytes. A nephrologist explains the concept of “The Great Dilution”—the dangerous process by which drinking too much water fundamentally alters your blood chemistry with potentially life-threatening results.
Under normal conditions, your kidneys maintain a very stable concentration of solutes (like sodium) in your blood plasma. This is called osmolality, and it’s a critical parameter for your health.
When you introduce an excessive amount of water into your system, you begin to dilute everything. The volume of plasma increases, but the amount of solutes remains the same. This causes the osmolality of your blood to drop. Your blood literally becomes more watery.
This dilution is the trigger for hyponatremia. The low concentration of sodium in the blood creates an osmotic gradient that forces water into your body’s cells, causing them to swell. This is the root cause of the condition’s dangerous symptoms.
The Great Dilution is a powerful illustration of why balance is more important than volume. Your health depends on the precise chemistry of your blood. Upsetting that chemistry by flooding it with water is a recipe for disaster. Drink to maintain balance, not to cause dilution.