The present disclosure is directed to methods for treating inherited or acquired mitochondrial disease using a cysteamine product, e.g., cysteamine or cystamine or derivatives thereof. It is contemplated that administration of the cysteamine product increases levels of free thiols in mitochondrial disease patients, which can improve the detrimental effects of respiratory chain dysfunction in patients. It is understood that such inherited or acquired mitochondrial disorders are due to inherited or acquired mutations in mitochondrial DNA or nuclear DNA used in mitochondria activity.
