Various devices, systems and methods for determining a parameter of and/or detecting chemical and biological substances in bodily fluid are described herein. A device or system may include a substrate. An active sensor having an electrical characteristic and/or a control sensor may be disposed on the substrate. In certain variations, a differential between a first signal from the active sensor, and a second signal from the control sensor may be used to determine a parameter of the chemical or biological substance in the sample of bodily fluid.
