In January 2007 a new research program was initiated at Uppsala University focusing on the biological applications of AMS. We have used a 5MV Pelletron Tandem accelerator to study biological samples. With Microdosing applications in mind, a variety of measurements have been performed on human blood, plasma and urine that have been labeled with a 14 C-labeled pharmaceutical drug covering a concentration range, spanning 3 orders of magnitude. Furthermore, by studying small sample amounts and low concentrations, we have demonstrated sensitivity in the hundred zeptomole range for a small pharmaceutical substance in human blood. Another application of interest, based on the enhanced 14 C activity from the cold war bomb-peak, is dating of DNA molecules providing fundamental data for the regenerative medicine and stem cell research community. We show data on a sensitive carrier method for measuring the isotopic ratio of small biological sample in the few μgC range.