ObjectiveThis study aims to investigate the plasma melatonin levels in systemic lupus erythematosus (SLE) patients and its relationship with clinical and laboratory features.Patients and methodsA total of 90 patients with SLE (82 females, 8 males; mean age 37.86 ± 13.98 years, range 19–77 years) and 90 healthy controls (82 females, 8 male; mean age 36.54 ± 10.89 years, range 22–60 years) were recruited for the current study. Plasma melatonin levels were detected by enzyme-linked immunosorbent assay.ResultsMelatonin levels were not significantly different in the plasma of patients with SLE compared with controls (P = 0.026). There was no significant difference regarding plasma melatonin level between SLE patients with nephritis and those without nephritis (P = 0.714); no significant difference was found between less active SLE and more active SLE (P = 0.791). The presence of IgM was associated with melatonin levels (P = 0.031) in SLE patients.ConclusionsThere is no significant difference in plasma melatonin levels between SLE patients and controls. Further studies are needed to elucidate the role of melatonin in SLE.