In contrast, the LN–SLE group exhibited lower eGFR (109.69 ± 39.10 vs. 144.26 ± 44.91 ml/min/1.73 m2, P = 0.032), complement C3 levels (0.71 ± 0.31 vs. 0.98 ± 0.34 mmol/L, P = 0.025), and 25(OH)-VD3 levels (9.91 ± 6.41 vs. 22.27 ± 9.98 μg/L, P < 0.001). Here, C3 is linked to systemic lupus erythematosus.