Total Body Water Content

Basic, Organ-Based and Clinical Sciences

Total body water (TBW) is defined as the volume of water in a person’s body, which can be calculated by multiplying the percentage of water content multiplied by kilogram weight. Typically, adult male weight is 60% water, adult female 50-55%. A 70kg adult has approximately 40L of total body water content. It varies based on age and adiposity. With increasing age, fatty tissue increases and TBW decreases. Females have more adipose tissue than males. TBW is highest in preterm (90%), full-term neonates (75-80%). In other words, neonates have a larger volume of distribution given their higher total body water content.

The components of Total Body Water are as follows:

Fluid as % of TBW (%)

Fluid as % of body weight (%)

Volume, in 70kg male (L)

Intracellular

67

40

28

Extracellular

- Interstitial

25

13

9

- Intravascular

8

7

5

TOTAL

100%

60%

42L

60%

Answered correctly

2019

Year asked

66%

Answered correctly

2017

Year asked

Author
Kamilla Esfahani, MD