Vitamin D review and supplementation recommendations for women diagnosed with breast or ovary cancer have been defined in the context of bone health and cancer prognosis/risk taking as reference wider cancer patients and postmenopausal women. This specific group has been selected due to its higher osteoporosis risk versus postmenopausal women. Early vitamin D supplementation could help maintain bone health, as well as potentially enhance cancer survival rate. Factors considered for supplementation include daily dose, periodicity, chemical form, administration, and serum levels. Sufficient vitamin D serum levels are recommended to be above 30 ng/ml (75 nmol/l). Maintenance oral supplementation equivalent to a minimum daily dosage of 800-1000 IU (20-25 μg) cholecalciferol provided in a daily to monthly bases is preferred, also advised to start with higher dosages when vitamin D serum levels are <10 ng/ml (25 nmol/l). Calcidiol supplementation is more effective, making it advantageous for cases with very low or difficult to raise vitamin D serum levels.