Leukopenia after the use of omeprazole may be associated with adverse drug reactions, infections, and immune system disorders. 1. Adverse drug reactions: a very small number of patients will have the adverse reaction of leukopenia after using omeprazole. 2. Infections: If the patient suffers from viral infections while using omeprazole, a drop in white blood cells may also occur. 3. Immune system disorders: leukopenia after using omeprazole may also be caused by immune system disorders such as systemic lupus erythematosus. There may be other reasons for white blood cell decline after using omeprazole, and patients are advised to go to the hospital in time for standardized treatment under the guidance of doctors.