Background Several studies propose that brain energy deficit might be partially involved in the pathophysiology of migraine. Previously, studies demonstrated that ketogenic diet causes a substantial reduction in migraine frequency. Since the ketogenic diet is restricting and its adherence is difficult, we proposed to supplement ketone bodies exogenously to provide a prophylactic effect in migraineurs. Aim To evaluate the prophylactic effect of exogenous DL-beta-hydroxybutyrate supplementation in episodic migraineurs. Methods A double-blind, placebo-controlled, randomised crossover trial was conducted, involving 41 patients with episodic migraine. Patients were randomised 1:1 into placebo or beta-hydroxybutyrate group before entering the first treatment period. Each treatment period was 12 weeks long, followed by four weeks of washout phase and four weeks of run-in phase before entering into the corresponding second treatment period. The primary endpoint was the number of migraine days in the last four weeks of treatment, adjusted for baseline. Results We observed no clinically significant amelioration of migraine frequency or intensity under DL-beta-hydroxybutyrate treatment as compared to placebo regarding number of migraine days (mean difference [95% CI]: −1.1[−5.07, 2.85]), migraine intensity (0–10 VAS: 1.5[−0.8, 3.7]). Conclusion The selected dose of supplemented exogenous DL-beta-hydroxybutyrate did not demonstrate efficacy in episodic migraineurs. ClinicalTrials.gov Identifier: NCT03132233