I went to the lab & results are: white blood cells: 6.79 10e3/ul red blood cells: 5.47 10e6/ul. mcv: 78.9 fl mch: 26.3 pg. rdw: 10.9% why is this low?

Many answers: One would want the hemoglobin and hematocrit levels to more accurately answer your question. The MCV above is borderline low based on a usual normal range that starts about 80. Low iron levels are the most common cause for a low mcv. I would have the complete blood count repeated before being overly worried about the above listed values.

See below: Agree with Dr. R. All laboratory results need to be interpreted in the clinical context and the doctor who ordered the tests is usually in the best position to do that. Talk to the doctor who ordered the tests. Having said that, if you are a woman, you may be iron deficient and may take oral iron and multivitamins. If you are male, do talk to your doctor soon.