TOTAL BODY WATER
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SUMMARY
TBW
1. In an adult male 18% of body weight (BW) is protein (& related substances), 7% mineral, 15% fat
2. Remaining 60% is water: total body water (TBW) is ~60% of his BW
3. TBW (60% of BW) = ECF (20% of BW or 14L) + ICF (40% of BW)
ECF
4. Remember: TBW = ECF + ICF, where ECF = interstitial fluid + plasma + lymph
5. 75% of ECF is in interstitial fluid (i.e. 15% of BW), 25% is in plasma (i.e. 5% of BW), only a negligible amount of lymph
6. Total blood volume (TBV) is 8% of BW
Reference(s)
Barrett, K.E., Barman, S.M., Brooks, H.L., X, J. and Ganong, W.F. (2019). Ganong’s review of medical physiology. 26th ed. New York: Mcgraw-Hill Education
