My wbc is at 17, 500. everything is normal including differential count. spleen and liver are ok. for 2 days i have been feeling tired. what could it b?

Too many to count: There isn't a simple answer to this question, because an elevated WBC is nonspecific, it can happen from just about any cause of inflammation or infection, or from other conditions of the blood-forming cells in the bone marrow.

Need more info: It is not feasible to provide a meaningful opinion without additional history, physical examination and may be some tests. With a total count of 17,500, some sub-types of WBC have to be out of normal range. It would have helped had you provided the numbers for the various types of WBC.