Vitamin D supports calcium absorption and bone metabolism, while vitamin K helps activate proteins that direct calcium to appropriate tissues (e.g., bone) and may limit calcium deposition in vessels (via MGP). This biological rationale drives interest in combined D+K strategies. Still, it is not automatically necessary for everyone: baseline levels, diet, risk factors, and clinical goals matter. Importantly, vitamin K supplements can interfere with anticoagulant therapy (e.g., warfarin), so combined use should be individualized and discussed with a clinician.