Stable isotopes are an established tool in speleothem science to reconstruct past climate variability. However, the interpretation of speleothem proxy signals is not straightforward, as the proxy signals are influenced by a variety of processes occurring in the atmosphere, soil and karst above the cave, as well as within the cave during precipitation of speleothem calcite. Non-traditional metal stable isotopes are a promising tool to further decipher the processes during speleothem formation. Due to recent developments in mass spectrometry, their application is now widely accessible. I will give an overview of the available non-traditional stable isotope systems and their application in speleothem research. In the second part of my talk, I will focus on stable Ca isotopes, which are a promising tool for quantitative reconstruction of prior calcite precipitation (PCP), a process in which Ca-carbonate is precipitated in air pockets in the host rock before it enters the cave, and which therefore strongly influences speleothem geochemistry. During my ongoing work, we are trying to reconstruct PCP on orbital time scales and compare contemporaneous interglacials in different cave systems and also different interglacials within the same cave system in Germany and Spain. In addition, a cave monitoring program is established to determine the modern-day Ca isotope fractionation factors between the host rock, cave drip water and modern calcite precipitates to ultimately quantify PCP and precipitation.