Objective: The aim of this study was to evaluate valproate dose association with weight change, blood glucose, lipid levels, and blood pressure in a psychiatric population. Methods: Data from 215 patients taking valproate for up to 1 year were collected from 2 longitudinal studies that monitored metabolic variables between 2007 and 2022. Linear mixed-effect models and logistic regressions were used to analyze the associations between valproate doses and metabolic outcomes. Results: An increase in valproate dose of 500 mg was associated with a weight change of +0.52% per month over a year (P < .001). The association between valproate dose and weight change was evident both before and after 3 months of treatment. Weight increase was greater for treatment durations of < 3 months compared to ≥ 3 months (+0.56%, P < .001 and +0.12%, P = .02 per month, respectively). Using piecewise regression, a significant association between dose and weight gain was observed in patients receiving doses equal to or above the median dose (1,300 mg/d), with a +0.50% increase in weight for each dose increment of 500 mg (P = .004). Among men, each 500 mg dose increment was associated with weight increases of +0.59% per month (P = .004), whereas a trend was observed for women (+0.40%, P = .09). No associations were found between valproate doses and blood glucose, lipid levels, or blood pressure over a 6-month treatment period. Conclusions: This study provides evidence that valproate dose, mainly for doses at or above 1,300 mg/d, is associated with weight gain in psychiatric patients, suggesting that the lowest effective doses should be prescribed to minimize weight gain.