To quantify health care utilization and costs by disease severity for patients with systemic lupus erythematosus (SLE) in the United States METHODS: We conducted descriptive analyses of Humedica electronic health record (EHR) data from 2011 to 2015 (utilization analysis) and integrated Optum administrative claims/Humedica EHR data from 2012 to 2015 (cost analysis) for patients with SLE. All-cause utilization outcomes examined were hospitalizations, outpatient visits, emergency department (ED) visits, and prescription drug use. Analyses of costs stratified by disease severity were limited to patients enrolled in an Optum-participating health insurance plan for ≥1 year after the earliest observed SLE diagnosis date. Costs were converted to 2016 US dollars.Health care utilization was evaluated in 17,257 patients with SLE. Averaged over the study period from 2011 to 2015, 13.7% of patients had ≥1 hospitalization per year, 25.7% had ≥1 ED visit, and 94.4% had ≥1 outpatient visit. Utilization patterns were generally similar across each year studied. Annually, 88.0% of patients had ≥1 prescription, including 1.3% who used biologics. Biologic treatment doubled between 2011 (0.7%) and 2015 (1.4%). Cost analyses included 397 patients. During 2012 to 2015, patients with severe SLE had mean annual costs of $52,951, compared with $28,936 and $21,052 for patients with moderate and mild SLE, respectively. Patients with severe SLE had increased costs in all service categories: inpatient, ED, clinic/office visits, and pharmacy.US patients with SLE, especially individuals with moderate or severe disease, utilize significant health care resources and incur high medical costs.