A new algorithm for evaluating patients suspected to have hemophagocytic lymphohistiocytosis (HLH) is available in the SLCH Lab Test Guidebook. This diagnostic approach was developed through collaborative efforts of hematology-oncology, rheumatology, PICU and lab medicine. Based on recent publications, this algorithm details a step-wise process for laboratory assessment and subspecialty consultation for patients with a clinical suspicion of HLH (i.e., patients with fever, splenomegaly, cytopenias and/or hepatitis of undetermined etiology). A new HLH lab order bundle has been added to KiDDOS. This algorithm and order set provide a uniform approach for the rapid diagnosis of HLH, which is critical for expedient initiation of appropriate therapy.