Hypernatremia caused by increased water loss can be due to which condition?

• A. Diabetes insipidus
• B. Renal tubular disorder
• C. Chronic diarrhea
• D. Profuse sweating

Answer: (A)

Hypernatremia from water loss happens when you lose more free water than you take in, so the sodium concentration in the blood rises. Diabetes insipidus disrupts the action of antidiuretic hormone, so the kidneys can't concentrate urine. That means a large amount of dilute urine is produced, leading to substantial free water loss. If water intake doesn’t keep up with those losses, plasma sodium increases, causing hypernatremia. The other scenarios involve fluid and electrolyte losses that aren’t characterized by large free-water losses with preserved or extended sodium retention, so they don’t produce the classic hypernatremia pattern seen with diabetes insipidus.