The estimated intravascular space in this example represents approximately what percent of body weight?

• A. 2.5%
• B. 5%
• C. 7.5%
• D. 10%

Answer: (B)

Intravascular space refers to the plasma portion of the extracellular fluid circulating in the vessels. In adults, plasma volume is typically about 4–5% of body weight, and exam practice often rounds this to 5%. That’s why the estimated intravascular space is about 5% of body weight. Total blood volume is a bit higher (around 7% of body weight), but the context here is plasma within the vasculature. So the best answer is the 5% option. The other numbers don’t match the usual plasma-volume fraction (2.5% is too low, 7.5% aligns more with whole blood volume, and 10% is above the typical plasma-range).