although astragalus supplements are generally well tolerated, mild gastrointestinal upset, diarrhea, and allergic reactions may occur. because astragalus may affect regulation of blood sugar and blood pressure, it may be risky for people with blood disorders, diabetes, or hypertension to use it as a supplement. astragalus may interact with prescribed drugs that suppress the immune system, such as medications used by people being treated for cancer or recovery from organ transplants.