A volume of an analyte-enriched fluid can be withdrawn out of a user's subcutaneous compartment using a patch unit that includes a reversible pumping mechanism. The volume can be withdrawn out of the body and into the patch unit through a cannula inserted into the subcutaneous compartment so that an analyte concentration in the volume can be measured using a sensing element within the patch unit. After analyte concentration analysis, at least the volume can be delivered back into the subcutaneous compartment by operating the pumping mechanism in a forward direction. biologically compatible fluid can optionally be pumped into the subcutaneous compartment from a reservoir in the patch unit and then allowed to partially or completely equilibrate with the analyte concentration in the interstitial fluid of the subcutaneous compartment via a permeable or semi-permeable cannula surface before being drawn back into the patch unit for analysis. Related systems, apparatus, methods, and/or articles are also described.