What's the cause for low white blood cell count?

Many causes.: Low WBC can be due to nutritional factors, infections (esp. Viral infections), autoimmune diseases, inhereted defects, leukemias and other bone marrow cancers, meylodysplasia, drug reactions, and even unknown causes. The problem with this is infection, but the risk depends on how low the WBC is. Only with very low WBC is there a risk of death.

Many causes.: Low WBC can be due to nutritional factors, infections (esp. Viral infections), autoimmune diseases, inhereted defects, leukemias and other bone marrow cancers, meylodysplasia, drug reactions, and even unknown causes. The problem with this is infection, but the risk depends on how low the WBC is. Only with very low WBC is there a risk of death.

Low white count: Causes include benign leukopenia, autoimmune diseases, rheumatoid arthritis, lupus, vasculitides, myelodysplastic syndrome, nutritional deficiencies like b12, copper deficiencies, medication effect etc. You need to see hematologist who can order blood tests and perform bone marrow aspirate and biopsy if indicated.