A lung fluid monitor monitors a fluid level in a lung and includes: a radiation source disposable on a first body surface and that produces nascent radiation, the nascent radiation: being received by the first body surface, communicated from the first body surface to a lung, attenuated proportionately to an amount of fluid in the lung, and communicated from the lung to a second body surface as attenuated radiation; a radiation detector disposable on the second body surface opposing the first body surface and in electromagnetic communication with the radiation source via the lung and that: receives the attenuated radiation from the lung and produces a detector signal from the attenuated radiation in response to receiving the attenuated radiation.