Astragalus (Astragalus membranaceus) is a traditional herbal remedy long used in Chinese medicine for its purported immunomodulatory and adaptogenic effects. Its use for radiation sickness stems primarily from Traditional Chinese Medicine (TCM) practices, where it is believed to "strengthen qi" and support the body's defense mechanisms against a broad range of stressors, including environmental toxins and radiation exposure. In TCM, astragalus is often included in herbal formulas aimed at supporting patients undergoing radiotherapy or those exposed to radiation, with the goal of reducing fatigue, supporting immune function, and aiding recovery.

The scientific evidence supporting astragalus for radiation sickness is limited. Some preclinical studies in animal models have suggested that extracts of astragalus may help mitigate radiation-induced damage, possibly through antioxidant effects, enhancement of hematopoiesis, and immunomodulation. For example, certain polysaccharides from astragalus have shown protective effects against bone marrow suppression and oxidative stress caused by radiation in animal studies. However, well-conducted clinical trials in humans are lacking, and the data from available studies are not robust enough to support routine clinical use for radiation sickness. Therefore, while astragalus use is justified by tradition and some promising preliminary research, it cannot currently be considered scientifically validated for this indication.