System for monitoring the hydration status of a living being by exploiting the modulation of backscattered RF electromagnetic waves from a wearable patched placed on the skin, said system comprising: a RF-tag adapted to be directly or indirectly fixed to the skin and containing at least one passive integrated circuit coupled to an antenna; an electromagnetic RF power source for supplying different signal frequencies to said RF-tag; a reader adapted to receive and to process the backscattered electromagnetic waves generated by said electromagnetic power source.