A non-invasive method of monitoring a biological parameter concerning a bodily
fluid of a subject, e.g., blood glucose of a human subject. The method includes:
placing an electrode against a site of the skin of the subject; measuring impedance
of the skin and determining the parameter therefrom; and using substantially the
same site in another determination. Another non-invasive monitoring method includes:
exposing a skin site to an aqueous salt solution for a pre-determined first period
of time; removing excess of the solution from the site; measuring impedance at
the site; exposing the site to the solution for a pre-determined second period
of time and repeating the removing and measuring steps. It is determined whether
the impedance measured falls within a pre-determined range. The latter exposure
and removal steps are repeated, if necessary, until two consecutive impedance measurements
within the pre-determined range are obtained.