Background <p>Glioblastoma multiforme (GBM) represents the most common and lethal primary brain tumor with incompletely understood pathogenesis. This study aims to systematically evaluate the causal relationships between blood metabolites and glioblastoma risk using Mendelian randomization approaches, providing metabolic biomarker evidence for disease prevention and early diagnosis.</p> Methods <p>Three Mendelian randomization analytical methods (inverse variance weighted, MR Egger regression, and weighted median) were employed to comprehensively assess causal relationships between multiple blood metabolites and glioblastoma. The study encompassed numerous metabolites including phospholipids, amino acid derivatives, vitamins, and carnitines. Multi-dimensional analytical approaches including forest plots, scatter plots, and funnel plots were used to evaluate effect estimates, dose-response relationships, and potential heterogeneity and pleiotropy bias.</p> Results <p>Among the multiple blood metabolites examined, most showed no significant causal relationship with glioblastoma risk. However, the study identified three key metabolites with significant protective effects: 1-linoleoyl-GPI, tryptophan betaine, and 1-stearoyl-2-oleoyl-GPE. Elevated blood levels of these metabolites demonstrated robust causal relationships with reduced glioblastoma risk, with consistent results across all three analytical methods and no significant horizontal pleiotropy or heterogeneity bias detected.</p> Conclusions <p>This study represents the first large-scale Mendelian randomization analysis to establish causal relationships between multiple blood metabolites and glioblastoma risk, particularly identifying protective factors within phospholipid and tryptophan metabolic pathways.</p>