Detailed definition
Vitamin D includes two main forms: D3 (cholecalciferol, made in skin from UVB exposure or from animal-source diet) and D2 (ergocalciferol, plant-source). Both are converted in the liver to 25-hydroxyvitamin D (25(OH)D, the storage form measured on lab panels) and then in the kidney to 1,25-dihydroxyvitamin D (calcitriol, the active hormone). Vitamin D is essential for intestinal calcium absorption and bone mineralization. Deficiency (25(OH)D < 20 ng/mL) and insufficiency (20–30 ng/mL) are common in midlife women, particularly those with limited sun exposure, darker skin, malabsorption, or obesity. Severe deficiency causes osteomalacia; lesser deficiency contributes to osteoporosis and fall risk. Bone Health Foundation and Endocrine Society recommend 800–2000 IU daily for postmenopausal women, with higher doses for documented deficiency.
Why it matters in menopause
Vitamin D adequacy is foundational alongside any bone-health strategy in menopause. ClearedRx may check 25(OH)D in women with bone-density concerns and recommend supplementation as needed.