Normal Rheumatoid Factor Levels Question If my lab results are <15.0 for my ra fact is this normal. And if not how much is it over the range. Thank you so much. Answer March 24, 2014 By Rebecca Manno, MD, MHS Normal range of Rheumatoid Factor level varies. Each laboratory has its own normal range depends on which assay they use. Most laboratory’s normal range is from 0.0 to 14.0. Any level higher than their normal range is abnormal.