An integrated device of a patch and sensor assembly detects extravasation or infiltration. A transmitter is positioned to direct power into a body portion. A sensor is positioned to receive the power transmitted through the body portion. A substrate is attachable to an outer surface of the body portion and supports the transmitter and the sensor. A signal processor is coupled to the transmitter and the sensor for detecting a change in a fluid level in the body portion from extravasation or infiltration based on the power received by the sensor. A power supply is coupled to the transmitter and the sensor. An indicator is responsive to the signal processor to indicate a detected change in a fluid level in the body portion from extravasation or infiltration.
