This article discusses the relationship between vitamin D and Hashimoto's thyroiditis (HT), an autoimmune disorder characterized by the immune system attacking the thyroid gland. Vitamin D is known for its immunomodulatory role, promoting immune tolerance. The study aims to review the connection between vitamin D status and HT, as well as the potential of vitamin D supplementation in reducing HT risk by modulating the immune system. Research indicates that HT patients often have lower vitamin D levels compared to healthy individuals, and vitamin D supplementation has been shown to decrease thyroid autoantibody titers in HT patients with vitamin D deficiency. However, more randomized, double-blind, placebo-controlled trials and longer follow-up periods are needed to fully understand the benefits of vitamin D in preventing and treating autoimmune thyroid diseases. The article also highlights the immunomodulatory effects of vitamin D on both innate and adaptive immune systems, emphasizing its role in regulating immune responses and potentially reducing the risk of autoimmune diseases. The review concludes that while vitamin D shows promise in managing HT, further research is necessary to establish its efficacy and optimal use in clinical practice.This article discusses the relationship between vitamin D and Hashimoto's thyroiditis (HT), an autoimmune disorder characterized by the immune system attacking the thyroid gland. Vitamin D is known for its immunomodulatory role, promoting immune tolerance. The study aims to review the connection between vitamin D status and HT, as well as the potential of vitamin D supplementation in reducing HT risk by modulating the immune system. Research indicates that HT patients often have lower vitamin D levels compared to healthy individuals, and vitamin D supplementation has been shown to decrease thyroid autoantibody titers in HT patients with vitamin D deficiency. However, more randomized, double-blind, placebo-controlled trials and longer follow-up periods are needed to fully understand the benefits of vitamin D in preventing and treating autoimmune thyroid diseases. The article also highlights the immunomodulatory effects of vitamin D on both innate and adaptive immune systems, emphasizing its role in regulating immune responses and potentially reducing the risk of autoimmune diseases. The review concludes that while vitamin D shows promise in managing HT, further research is necessary to establish its efficacy and optimal use in clinical practice.