An exemplary implantable microarray device includes an inlet for a body fluid, a plurality of individual reaction cell arrays where each reaction cell array includes a series of reaction cells configured to receive the body fluid, a sensor array to sense a reaction result for an individual reaction cell array where the reaction result corresponds to a reaction between the body fluid and at least one reagent in each of the reaction cells of the individual reaction cell array and a positioning mechanism to position an individual reaction cell array with respect to the sensor array. Various other exemplary technologies are also disclosed.