Short Description of the Paper The experimental appraisal of existing molecular communication (MC) testbeds and modeling frameworks in real blood is an important step for future Internet of bio-nano-things applications. In this work, we experimentally compare the MC flow characteristics of water, blood substitute, and real porcine blood for a previously presented superparamagnetic iron oxide nanoparticles (SPION) MC testbed. We perform an extensive analysis of the system impulse response behavior of the testbed for the different fluids. Based on the identified MC flow characteristics, we extend a mathematical framework to capture the flow properties of blood and evaluate its applicability. In our evaluation, we see that the added complexity of the transmission in blood opens up promising new possibilities to improve communication through the human circulatory system. Data and Code We publish our experimental data and the Python code to process it as described in the paper here on Zenodo and in an accompanying GitHub repository under the CC BY and MIT licenses, respectively.In addition to the source data, we provide a visual overview of the collected measurements for all configurations in the file supplementary_data_overview.pdf. Contact If you have any questions or suggestions for improvements, feel free to contact us. Lisa Y. Debus Email: debus@ccs-labs.org Henri Wolff Email: henri.wolff@charite.de Luiz C. P. Wille Email: luiz.wille@fau.de