Vitamin D

Vitamin D is a fat-soluble nutrient that functions as both a vitamin and a hormone, playing critical roles in calcium absorption, immune function, mood regulation, and reproductive health. Deficiency is remarkably common in women with PCOS, affecting approximately 67-85% of those diagnosed, and low vitamin D levels are associated with worsened insulin resistance, increased inflammation, and poorer fertility outcomes. Supplementation (typically 1,000-4,000 IU daily, guided by blood level testing) has been shown to improve ovulation rates, reduce androgen levels, decrease inflammatory markers, and enhance the effectiveness of other PCOS treatments including fertility medications.