what is biva?

BIVA is a way of interpreting the data obtained from Bioelectrical Impedance Analysis (BIA) devices. It is a quick and easy way of discovering an individual’s hydration and nutritional status in comparison to their demographic group. BIVA stands for Bioelectrical Impedance Vector Analysis and is sometimes referred to as the ‘Rxc Graph’. There are no complex mathematical equations involved in BIVA technology, it simply uses the Resistance(R) and Reactance (Xc) at 50 kHz and is normalised to the subject’s height. Once the measurement is taken, the subject’s results are displayed in the form of a dot on the vector. The position of the dot then reflects the subject’s health status against their chosen demographic group.

biva graphical representation

graphical representation

This graph displays a subject’s tests over time (blue markers). The desired outcome for a physician is a mark within the 75% tolerance (the middle of the 3 tolerance lines) range of the statistic distribution for the chosen demographic group.

The line from the point of origin indicates the Vector Length. The shorter this line, the more fluid overload or oedema is present. The longer the line, the more dehydration is present in the subject. The angle of the vector also has significance. The steeper the angle, the more athletic or obese the subject is, whereas a shallow angle reflects malnourishment or anorexia.


There are many advantages with the use of a BIVA graph. The measurement is very simple, requiring only the height, gender and population group of the subject. BIVA enables a subject’s hydration or BCM status to be evaluated based on raw data alone, independently of complex mathematical calculations, making it fantastic for research applications. The BIVA graph is also incredibly accurate, giving physicians the confidence that results are accurate.

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