In patients with uncontrolled diabetes, why is dehydration common?

• A. Osmotic diuresis from high blood glucose causes water loss
• B. Decreased urine production
• C. Increased intestinal absorption of water
• D. Improved kidney function

Answer: (A)

High blood glucose in uncontrolled diabetes overwhelms the kidneys’ ability to reabsorb it. When glucose spills into the urine (glucosuria), it raises the urine’s osmolarity and draws water with it. This osmotic diuresis increases urine volume, leading to significant water loss and dehydration. This mechanism directly explains why dehydration is common in uncontrolled diabetes.

The other ideas don’t fit the situation: decreased urine production would not cause dehydration, since urine output is actually increased; increased intestinal absorption of water would help retain water rather than lose it; and simply having “improved kidney function” would not produce the water loss seen with osmotic diuresis.