D dimer was .39 a month ago and .49 yesterday. is this anything to worry about or normal fluxuation? less than .50 is normal

Normal range:95%rule: Most laboratories define the 'normal' range to be the values randomly seen in 95% of normal individuals. This reflects the natural variations seen in a given test, and differences between individuals. In your case, you are in the high end of the 95% bell curve of normal individuals. D-Dimer may also randomly increase for various reasons. That is why your doc needs to interpret the test.