The severity of signs and symptoms of radiation sickness depends on how much radiation you've absorbed. How much you absorb depends on the strength of the radiated energy, the time of your exposures, and the distance between you and the source of radiation. Signs and symptoms are also affected by the type of exposure — such as total or partial body. The severity of radiation sickness also depends on how sensitive the affected tissue is. For instance, the gastrointestinal system and bone marrow are highly sensitive to radiation. Initial signs and symptoms The initial signs and symptoms of treatable radiation sickness are usually nausea and vomiting. The amount of time between exposure and when these symptoms develop is a clue to how much radiation a person has absorbed. After the first round of signs and symptoms, a person with radiation sickness may have a brief period with no apparent illness, followed by the onset of new, more-serious symptoms. If you've had a mild exposure, it may take hours to weeks before any signs and symptoms begin. But with severe exposure, signs and symptoms can begin minutes to days after exposure. Possible symptoms include:  Nausea and vomiting Diarrhea Headache Fever Dizziness and disorientation Weakness and fatigue Hair loss Bloody vomit and stools from internal bleeding Infections Low blood pressure 
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radiation sickness