What are the consequences of dehydration on blood concentration?

• A. Hemoconcentration, hypovolemia, and hyperviscosity.
• B. Decreased hematocrit and increased plasma volume.
• C. Increased blood flow to tissues.
• D. No change in viscosity.

Answer: (A)

Dehydration raises the concentration of blood components by removing free water from plasma, which leads to hemoconcentration—the rise in the relative amounts of red cells and plasma proteins. As fluid volume decreases, overall circulating blood volume becomes insufficient, producing hypovolemia. With more cells and proteins in a smaller volume, the blood becomes thicker, causing hyperviscosity. This combination—hemoconcentration, reduced blood volume, and increased viscosity—fits the described consequences of dehydration.

That’s why this option is best: it reflects the expected changes in hematocrit (increased), plasma volume (decreased), and viscosity (increased). Dehydration does not cause decreased hematocrit or increased plasma volume, nor does it leave viscosity unchanged; those would contradict the fluid-loss effects.