In a typical adult, intracellular fluid accounts for approximately what fraction of total body water?

In a typical adult, intracellular fluid accounts for approximately what fraction of total body water?

• A. 25%
• B. 40%
• C. 55%
• D. 70%

Answer: (C)

The key idea is how body water is distributed between two major compartments: inside cells and outside cells. In a typical adult, total body water is about 60% of body weight. The intracellular fluid makes up about 40% of body weight, which is roughly two-thirds of the total body water. That means intracellular fluid is about 66–70% of TBW, so the closest estimate is around 70%. The extracellular fluid then accounts for the remaining roughly one-third of TBW. So, saying intracellular fluid is around two-thirds to three-quarters of TBW aligns with the standard distribution, making approximately 70% the best approximate fraction.

The key idea is how body water is distributed between two major compartments: inside cells and outside cells. In a typical adult, total body water is about 60% of body weight. The intracellular fluid makes up about 40% of body weight, which is roughly two-thirds of the total body water. That means intracellular fluid is about 66–70% of TBW, so the closest estimate is around 70%. The extracellular fluid then accounts for the remaining roughly one-third of TBW. So, saying intracellular fluid is around two-thirds to three-quarters of TBW aligns with the standard distribution, making approximately 70% the best approximate fraction.