Thiamine (vitamin B1) is key in maintaining cellular health and energy metabolism. Thiamine is required for proper functioning of enzymes involved in glucose metabolism, which is critical for providing energy to cells. This energy is essential for various cellular processes, including DNA repair mechanisms. In addition, it is a prerequisite for the functioning of key enzymes in the biosynthesis of pentose sugars, which are essential in the synthesis of nucleic acids. Additionally, thiamine has antioxidant properties that help reduce oxidative stress in cells; thus, by relieving this stress, thiamine indirectly supports the maintenance of DNA integrity. Ensuring adequate thiamine intake through diet or supplements can support overall cellular health and potentially aid in DNA repair processes. This review aims to highlight the essential role of vitamin B1 in supporting metabolic health, especially given that deficiencies can develop in patients with disease-related malnutrition as well as in those with an inadequate diet.