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 volume in fluid communication with the proximal openings of the tissue piercing elements; sensing fluid extending into the sensing volume; and a glucose sensor adapted to detect a concentration of glucose in the sensing fluid within the sensing volume. Another aspect of the invention provides A method of in vivo monitoring of an individual's interstitial fluid glucose concentration comprising: inserting distal ends of a plurality of tissue piercing elements through a stratum corneum area of the individual's skin, the tissue piercing elements each comprising a distal opening, a proximal opening, and an interior space extending between the distal and proximal opening; allowing interstitial fluid to flow into the interior space of the tissue piercing elements to substantially fill the interior space; filling substantially the entire interior space of the sensing area; and sensing a glucose concentration of the sensing fluid.