The monitoring of specific molecules in the living body has historically required sample removal (e.g., blood draws, microdialysis) followed by analysis via cumbersome, laboratory-bound processes. Those few exceptions to this rule (e.g., glucose, pyruvate, the monoamines) are monitored using "one-off" technologies reliant on the specific enzymatic or redox reactivity of their targets, and thus not generalizable to the measurement of other targets. In response we have developed in vivo electrochemical aptamer-based (E-AB) sensors, a modular, receptor-based measurement technology that is independent of the chemical reactivity of its targets, and thus has the potential to be generalizable to a wide range of analytes. To further the adoption of this in vivo molecular measurement approach by other researchers and to accelerate its ultimate translation to the clinic, we present here our standard protocols for the fabrication and use of intravenous E-AB sensors.