Time Phases of Acute Radiation Syndrome (ARS) - Dose Range 2-4 Gy
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Dose Range in gray (Gy)
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Data adapted from:
Diagnosis and Treatment of Radiation Injuries
(PDF - 202 KB)
(IAEA Safety Reports Series No. 2, Vienna 1998)

Timeline: 2-4 Gy

Acute Radiation Syndrome time phases resulting from 2-4 Gy radiation expoure Next

ARS time phases and approximate whole body dose from exposure: 2-4 Gy

Manifest Illness
Prodromal Latent Manifest Illness (Critical Phase) Recovery or Death
bar chart of subsyndrome severity of hematopoietic, gastrointestinal, and neurovascular subsyndromes
bar chart legend
  • Onset: 1-2 hours after exposure
  • Percent of victims who vomit at this dose: 70-90%
  • None in some patients, mild in others at the higher end of the dose range.
  • Mild
Level of consciousness
  • Unaffected
Body temperature
  • Increased
  • Onset: 1-3 hours after exposure
  • Percent of victims with fever at this dose: 10-80%
Medical response
  • Observation in general hospital, especially for those at higher end of this dose range
  • Treatment in specialized hospital as needed and feasible
  • From end of prodrome through day 18-28
  • Moderate hair loss, beginning on day 15 or later
Medical response
  • Hospitalization recommended if feasible
  • 18-28 days after prodrome
  • Weeks to months
Possible clinical effects
  • Anorexia
  • Fever
  • Malaise, weakness
  • Bleeding, infection
  • Epilation
  • Diarrhea: none to mild at lower end of dose range; more severe with increased dose from exposure
Medical response
  • Appropriate supportive care
  • Rare in the lower end of this dose range
  • Up to 50% may die at higher end of this dose range at 6-8 weeks.
  • Aggressive supportive care will salvage many patients at the high end of this dose range.
  • Depends on GI and bone marrow recovery
  • All victims require surveillance for late effects
  • Psychological support helpful
Time to recovery
  • Weeks to months
  • Potentially avoidable with appropriate supportive care unless severe complications develop