The new EU in vitro diagnostic medical devices regulation (IVDR) extends to medical use of in vitro diagnostics (IVDs) in clinical trials, in addition to marketed IVDs. Although compliance to some aspects has been required since the Date of Application on 26 May 2022, there has been limited guidance issued to clarify IVDR requirements for use of IVDs in clinical trials. This has led to differences in interpretation between IVD manufacturers, investigational drug sponsors, ethics committees and regulators across Europe, resulting in delays to initiation of clinical trials. A coordinated consultation process is urgently needed, alongside clear guidance on the interface between the Clinical Trial Regulation (CTR) and IVDR, to address the difficulties faced by sponsors of combined drug and IVD studies in Europe.