Introduction: SLE is still a disease with a high morbidity and mortality, where clinical syndrome occur due to immune system dysregulation and are characterized by the formation of antinucleous autoantibodies (ANA), especially anti-doublestranded DNA (antids-DNA) which subsequently form immune complexes and inflammation and tissue damage. Lately there have been many studies on Procalcitonin (PCT) as inflammatory marker. Aim: to assess differences in serum procalcitonin levels between SLE mild, moderate and severe. Methods: This is an observational study with cross sectional design in SLE patients at Haji Adam Malik Central Hospital (RSUP HAM) Medan from January 2016 to December 2018. The patients were divided into three degrees based on clinical manifestations: mild, moderate and severe SLE. Use Kruskal wallis to find the difference the procalcitonin level between mild, moderate, and severe. Using SPSS version 22.0, with the value p <0.05 was significant. Results: 157 SLE patients age > 18 years, SLE without infection 118 (75.2%). Distribution of respondents based on SLE severity Level Mild (34), Moderate (30), Severe (54). Mean and Standard deviation of PCT levels at each degree of SLE in a sequence are mild (0.17 ± 0.34), increasing at a moderate level (0.24 ± 0.19) and the greatest result at a severe degree (1,13 ± 2.93). Based on bivariate analysis with Kruskal-Wallis from differences PCT levels between SLE mild, moderate, and severe showed statistical significance (p = 0.014). Conclusion: Based on the increase in PCT levels along with an increase in the severity of SLE non-infectious, statistically there is a significant difference.