(covers information from several alternate timelines)
This page contains information regarding new Star Trek material, and thus may contain spoilers.
Radiation poisoning (or radiation sickness) is a form of organic tissue damage caused by exposure to ionizing radiation. Symptoms vary with the severity of exposure but often include fatigue, nausea, vomiting, and hair loss. Radiation may cause sterility and cancer, and, given a large enough dose, can be lethal. Its effects can be countered for a short time with hyronalin, though adrenaline was once a treatment as well. Extreme cases of theta radiation poisoning can be treated with arithrazine. (VOY: "The Omega Directive") By the 24th century, cellular damage by radiation could be prevented by taking special inoculations. Radiation poisoning can also lower calcium levels. (DS9: "Visionary") Exposure to delta radiation also causes severe disfigurement, which could be considered a form of radiation poisining as well. (ENT: "In a Mirror, Darkly", TOS: "The Menagerie, Part I")
In 2063, Lily Sloane was affected by theta radiation poisoning. It came from the Phoenix's throttle assembly, which was damaged by the Borg's attack on Bozeman, Montana. Dr. Beverly Crusher later treated her condition on the USS Enterprise-E. (Star Trek: First Contact)
In 2285, after repairing the USS Enterprise's warp drive and allowing it to escape Khan Noonien Singh's detonation of the Genesis Device, Captain Spock was affected by radiation poisoning and eventually died from it. (Star Trek II: The Wrath of Khan)
In 2259 of the alternate reality, Kirk and Spock's positions were reversed during their confrontation with Khan: Kirk poisoned himself repairing the USS Enterprise's warp core before the ship crashed to Earth. Fortunately, Spock apprehended Khan and Leonard McCoy performed a blood transfusion to revive Kirk. (Star Trek Into Darkness)
In 2370, the debris from a crash landed Federation probe caused radiation poisoning within the Barkonians on Barkon IV. Lieutenant Commander Data was able to get a cure and administered it into the community well. (TNG: "Thine Own Self")