Classification of acute radiation sickness according to radiation dose.
| Radiation dose (in Gray* ) | Rating | Effect of irradiation |
| up to 0,2 | Possible assumed late effects: Tumor diseases (cancer), changes in the genome (genetic alterations). | |
| 0,2-0,5 | No clinical symptoms; laboratory evidence of erythrocytopenia (decrease in red blood cells) | |
| 1 -2 | Mild radiation sickness | 10% deaths after 30 days (Lethal Dose (LD) 10/30)mild to moderate nausea (50% likely at 2 Sv) with occasional vomiting |
| 2-4 | Severe radiation sickness | 35-50% deaths after 30 days (LD 35/30)Leukopenia (decrease in white blood cells) and rapid increase in risk of infection |
| 4-6 | Most severe radiation sickness | 60% deaths after 30 days (LD 60/30)usually only symptoms of the hematopoietic system (infections, bleeding) |
| 6 – 10 | 100% deaths after 14 days (LD 100/14)the bone marrow is completely destroyed | |
| > 10 and < 20 | 100% deaths after 7 days (LD 100/7)massive diarrhea (diarrhea), intestinal bleeding and water loss, and electrolyte imbalance; death occurs with febrile delirium and coma from circulatory failure | |
| ≥ 20 and < 50 | 100% deaths after 3 days (LD 100/3)in addition to the symptoms listed above, neurological symptoms may also occur | |
| ≥ 50 | Immediate disorientation and coma within seconds or minutes; death occurs in a few hours |
* One gray (Gy) is identical to one sievert (= 1 joule per kg) for x-rays, gamma, and beta radiation.