Continuous analyte measurement systems and systems and methods for implanting them

A analyte monitoring system, comprising:

• a base unit configured for mounting on a skin surface;
• an analyte sensor comprising a proximal portion configured to be coupled to the base unit and a distal portion configured to be inserted through the skin surface and in contact with a bodily fluid, wherein the analyte sensor is configured to generate electrical signals indicative of levels of an analyte in the bodily fluid, wherein the distal portion comprises:
• a plurality of electrodes comprising a working electrode,
• an analyte responsive enzyme layer on the working electrode, and
• a first membrane layer on the analyte responsive enzyme layer configured to modulate a flux of the analyte to the analyte responsive enzyme layer,
• wherein the sensor is configured to provide for perpendicular and lateral diffusion of the analyte through the first membrane layer to the analyte responsive enzyme.