What Causes Elevated Levels Of WBC?

I got results from the lab today..my hemoglobin is 10.5..... hematocrit 32.8.........mcv 73.8........mch.......23.7.........mchc.......32........rdw......15.6.....my Dr wants me to supplement with iron and no other testing for 3 months...is this common.my wbc is a10.3.