Background - A recent controlled trial suggested that high-dose biotin supplementation reverses disability progression in patients with progressive multiple sclerosis. Objective - To analyze the impact of high-dose biotin in routine clinical practice on disability progression at 12 months. Methods - Progressive multiple sclerosis patients who started high-dose biotin at Nantes or Rennes Hospital between 3 June 2015 and 15 September 2017 were included in this prospective study. Disability outcome measures, patient-reported outcome measures, relapses, magnetic resonance imaging (MRI) data, and adverse events were collected at baseline, 6, and 12 months. Results - A total of 178 patients were included. At baseline, patients were 52.0 ± 9.4 years old, mean Expanded Disability Status Scale (EDSS) score was 6.1 ± 1.3, mean disease duration was 16.9 ± 9.5 years. At 12 months, 3.8% of the patients had an improved EDSS score. Regarding the other disability scales, scores either remained stable or increased significantly. In total, 47.4% of the patients described stability, 27.6% felt an improvement, and 25% described a worsening. Four patients (2.2%) had a relapse. Of the 74 patients (41.6%) who underwent an MRI, 20 (27.0%) had new T2 lesions, 8 (10.8%) had gadolinium-enhancing lesions. Twenty-five (14%) reported adverse event. Conclusion - In this study, high-dose biotin did not seem to be associated with a clear improvement in disability.