BackgroundFlare-up of systemic lupus erythematosus (SLE) is a common characteristic that could have deleterious effects on patients’ outcome and survival. The aim of this study was to identify the predictors of severe lupus flare.Methods120 patients with SLE were enrolled and followed-up for 23 months. Demographic, clinical manifestations, laboratory parameters and disease activity were recorded at each visit. In addition, presence of severe lupus flare at each visit was evaluated by using the Safety of Estrogens in Lupus Erythematosus National Assessment (SELENA)-SLE disease activity index (SLEDAI) flare composite index. Predictors of severe lupus flare were obtained by backward logistic regression analyses. Predictors of SLEDAI were obtained by backward linear regression analyses.ResultsDuring the follow-up period, 47 patients had at least one episode of severe lupus flare. Mean (SD) age of patients with severe flare versus no flare was 31.7 (7.89) and 38.3 (8.24) years, respectively (P = 0.001). Ten (62.5%) out of 16 males and 37 (35.5%) out of 104 females had severe flare (P = 0.04). History of lupus nephritis (LN) was recorded in 76.5% and 44% of patients with severe flare and no severe flare, respectively (P = 0.001). Thirty-five (29.2%) patients with high anti-double-stranded DNA (anti-ds-DNA antibody) and 12 (10%) with negative anti-ds-DNA antibody had severe lupus flare (P = 0.02). By multivariable logistic regression analysis, younger age (OR = 0.87, 95% CI 0.80–0.94, P = 0.0001), history of LN (OR = 4.66, 95% CI 1.55–14.002, P = 0.006) and high SLEDAI at the first visit (OR = 1.19, 95% CI 1.026–1.38) were the main predictors of flare. When severe lupus flare after the first visit was used as the outcome variable, similar findings were observed but, SLEDAI, although left among the final predictors in the model, was not significant. SLEDAIs in future visits were mainly predicted by Anti-ds-DNA antibody, 24-h urine protein and arthritis at the first visit.ConclusionSLE patients with younger age, history of previous LN or high baseline SLEDAI, may need closer monitoring and follow up.Supplementary InformationThe online version contains supplementary material available at 10.1186/s41927-023-00333-y.