The total body water can be estimated from the total body weight, age and gender of the patient.
Approximate Percentage of Total Body Weight Consisting of Total Body Water
|
Age in Years
|
Male
|
Female
|
|
0 - 1
|
80%
|
75%
|
|
1 - 5
|
65%
|
65%
|
|
6 - 9
|
|
|
|
10 - 16
|
60%
|
60%
|
|
17 - 39
|
60%
|
50%
|
|
40 - 59
|
55%
|
47%
|
|
>= 60
|
50%
|
45%
|
from West (1991)
total body water in liters =
= (percent based on age and gender) * (body weight in kilograms)
where:
• In the elderly and in cachexia, 50% may be used.
• Fat has little water, so lean body weight should be used for the calculation.
