OBJECTIVE: The aim was to describe direct health-care costs for adults with SLE in the UK over time and by disease severity and encounter type. METHODS: Patients aged ≥18 years with SLE were identified using the linked Clinical Practice Research Datalink-Hospital Episode Statistics database from January 2005 to December 2017. Patients were classified as having mild, moderate or severe disease using an adapted claims-based algorithm based on prescriptions and co-morbid conditions. We estimated all-cause health-care costs and incremental costs associated with each year of follow-up compared with a baseline year, adjusting for age, sex, disease severity and co-morbid conditions (2017 UK pounds). RESULTS: We identified 802 patients; 369 (46.0%) with mild, 345 (43.0%) moderate and 88 (11.0%) severe disease. The mean all-cause cost increased in the 3 years before diagnosis, peaked in the first year after diagnosis and remained high. The adjusted total mean annual increase in costs per patient was £4476 (95% CI: £3809, £5143) greater in the year of diagnosis compared with the baseline year (P < 0.0001). The increase in costs per year was 4.7- and 1.6-fold higher among patients with severe SLE compared with those with mild and moderate SLE, respectively. Primary care utilization was the leading component of costs during the first year after diagnosis. CONCLUSION: The health-care costs for patients with SLE in the UK are substantial, remain high after diagnosis and increase with increasing severity. Future research should assess whether earlier diagnosis and treatment might reduce disease severity and associated high health-care costs.