[en] The biomedical program at PRIME Lab has prepared radiocarbon and "4"1Ca as tracers for a variety of applications. Over the last decade several hundred "1"4C samples and several thousand "4"1Ca samples have been measured per year. Biomedical samples pose challenges that are relatively rare in the AMS community. We will discuss how to prepare and compensate for samples that have isotope ratios above the dynamic range of AMS, high interference rates, and small samples sizes. In the case of "4"1Ca, the trade off in the chromatography between yield and sample cleanliness will be analyzed. Secondary standards that have isotope ratios commonly encountered in our applications are routinely prepared. We use material from the Joint Research Centre’s Institute for Reference Materials and Measurement: IRMM-3701/4, 3701/5, and 3701/6 and a standard produced by PRIME Lab for "4"1Ca. We use International Atomic Energy Agency’s IAEA C-3, IAEA C-7, IAEA C-8, and a ∼12.5× modern oxalic acid secondary standard supplied by Lawrence Livermore National Laboratory for "1"4C. We will discuss our precision, reproducibility, and the relative agreement between our measured and the reported values for these materials.