Background <p>Recent research highlights a growing link between metabolic dysregulation—particularly involving glucose and lipid metabolism—and suicidal ideation. Given the potential role that carbohydrate and fat metabolism play in suicidal ideation, it is essential to conduct a thorough examination of their joint effects. The triglyceride-glucose (TyG) index, an innovative indicator assessing insulin resistance and overall metabolic status, shows promise in predicting mental health issues related to metabolic disorders. The purpose of this study was to explore the relationship between Tyg index and suicidal ideation and its influencing factors.</p> Methods <p>Our study analyzed data from the National Health and Nutrition Examination Survey, covering the period from 2009 to 2018. The TyG index was derived using the equation: Ln [fasting triglycerides (mg/dL) × fasting glucose (mg/dL) / 2]. The ninth item of the Patient Health Questionnaire-9 gauged ideations of suicide. Using modified multivariable logistic regression, the relationship between the TyG index and ideation of suicide was investigated in further detail. The nonlinearity was managed using smooth curve fitting, and the threshold effects of these nonlinear relationships were further investigated using a two-part linear regression model. Subgroup and interaction analyses were also performed to test the robustness of the results. Subgroup analyses were conducted by race, body mass index, and hypertensive status, while interaction terms were used to assess potential effect modification.</p> Results <p>Among the 11,551 individuals in the study, 3.55% reported experiencing suicidal ideations. Significant differences (<i>P</i> &lt; 0.05) were observed in the following domains: race, degree of education, body mass index, income, diabetes, elevated blood pressure, and depressive symptoms between the groups with and without suicidal ideation. A Strong nonlinear correlation was found between suicidal ideation and an elevated TyG index; a fully adjusted model revealed a 27% increased likelihood per unit increase. In the hypertensive group, a nonlinear relationship was noted, with a threshold effect at a TyG index of 8.75. Subgroup analysis and interaction tests revealed variations in this association, particularly by race and body mass index. There was a significant positive association in obese people, but not in other groups.</p> Conclusions <p>The study determined that an elevated TyG index may influence suicidal ideation, particularly underscoring the need for targeted interventions and routine metabolic and mental health screenings, especially in high-risk groups like obese and hypertensive individuals.</p>