one aspect of the invention provides a glucose monitor having a plurality of tissue piercing elements , each tissue piercing element having a distal opening , a proximal opening and interior space extending between the distal and proximal openings ; a sensing area in fluid communication with the proximal openings of the tissue piercing elements ; sensing fluid extending from the sensing area into substantially the entire interior space of the tissue piercing elements ; and a glucose sensor adapted to detect a concentration of glucose in the sensing fluid within the sensing area . another aspect of the invention provides a method of in vivo monitoring of an individual &# 39 ; s interstitial fluid glucose concentration including the following steps : inserting distal ends of a plurality of tissue piercing elements through a stratum corneum area of the individual &# 39 ; s skin , the tissue piercing elements each having a distal opening , a proximal opening , an interior space extending between the distal and proximal openings , and a sensing fluid filling substantially the entire interior space ; and sensing a glucose concentration of the sensing fluid .