Background <p>Patients on dialysis often suffer from carnitine deficiency due to reduced intake, reduced synthesis in the kidneys, and clearing through dialysis. Carnitine deficiency may lead to anemia, cardiomyopathy, hypotension, and so on. Several studies have shown that supplementing with L-carnitine can diminish the above symptoms in adult dialysis patients, but whether children can benefit from L-carnitine remains unclear.</p> Objectives <p>This study was performed to investigate the effect of L-carnitine in children with kidney failure undergoing dialysis.</p> Data sources <p>PubMed, Embase, The Cochrane Library, China National Knowledge Infrastructure (CNKI), WanFang Data, and VIP database were electronically searched from database inception to December 2023.&#xa0;</p> Study eligibility criteria <p>We included randomized controlled trials (RCTs), cohort studies, case–control studies, cross-section studies, and case series studies that evaluated the impact of L-carnitine on children.</p> Participants and interventions <p>Patients aged less than 18&#xa0;years with kidney failure undergoing dialysis.&#xa0;</p> Study appraisal and synthesis methods <p>We assessed the quality of studies using the RoB2 tool recommended by the Cochrane Handbook, the Newcastle–Ottawa Quality Assessment Scale (NOS), the checklist recommended by Agency for Healthcare Research and Quality (AHRQ), and the quality evaluation tool recommended by the National Institutes of Health (NIH). We conducted only descriptive analyses and did not perform meta-analysis due to significant differences in study types and limited data.</p> Results <p>A total of 194 patients were included in 9 studies, of which 3 were RCT studies; 2 were cohort studies, and 4 were case series studies. Due to limited data, we only conducted descriptive analysis rather than meta-analysis. For children undergoing hemodialysis, cohort study of high-quality showed that L-carnitine significantly improved hemoglobin (Hb) and reduced the required erythropoiesis-stimulating agent (ESA) dose; RCT study of moderate-quality indicated that L-carnitine did not influence serum lipid profiles except for reducing apolipoprotein B (ApoB). Cohort study of moderate-quality showed that L-carnitine improved cardiac function; RCT study of moderate-quality indicated that L-carnitine did not influence albumin, C-reactive protein (CRP), interleukin-6 (IL-6), and quality of life. For children undergoing peritoneal dialysis, only serum lipid profiles were analyzed. RCT and case series studies of moderate-quality indicated that L-carnitine did not influence serum lipid profiles except for reducing ApoB.</p> Limitations <p>The number of studies enrolled was limited, and their quality was not high.</p> Conclusions and implications of key findings <p>Our study found that children with kidney failure requiring dialysis could partially benefit from L-carnitine, including increased Hb, decreased ESA requirement, reduced ApoB, and improved cardiac function. Further RCTs of high quality are still needed to clarify this issue. This study provided more comprehensive and credible evidence for clinical use of L-carnitine in children.</p> Registration number <p>PROSPERO registration number CRD420250649553.</p> Graphical Abstract <p></p>