Vitamin D and Vitamin K2 Supplementation Guidelines

Introduction to Vitamin Supplementation

The American Journal of Kidney Diseases recommends that patients on warfarin or other vitamin K antagonist anticoagulants must not receive vitamin K supplements of any form, including K2, as this directly interferes with anticoagulant efficacy and creates serious risk of thromboembolism 1

The American Journal of Kidney Diseases and Praxis Medical Insights state that this contraindication applies to all forms of vitamin K, including K1 and K2, and patients on warfarin should maintain consistent dietary vitamin K intake rather than supplementing 1, 2

Praxis Medical Insights recommends the standard evidence-based regimen for documented vitamin D deficiency is cholecalciferol 50,000 IU once weekly for 8-12 weeks, followed by maintenance therapy of 800-2,000 IU daily 3, 4
The American College of Cardiology is not mentioned, however Praxis Medical Insights suggests vitamin D3 is strongly preferred over D2 because it maintains serum levels longer and has superior bioavailability 4

The American Journal of Kidney Diseases recommends that for CKD stages 3-4, standard nutritional vitamin D replacement with cholecalciferol or ergocalciferol should be used, not active vitamin D analogs 1, 3, 4
Praxis Medical Insights suggests that a minimum of 800 IU daily is recommended for elderly patients even without baseline measurement, as this population has decreased skin synthesis and higher fall/fracture risk 3, 4

Clinical Nutrition and Praxis Medical Insights state that daily doses up to 4,000 IU are consistently recognized as safe for adults across all major guidelines, with no risk of toxicity when used long-term 4, 5
Praxis Medical Insights notes that vitamin D toxicity is rare but can occur with prolonged daily doses exceeding 10,000 IU or serum levels above 100 ng/mL, manifesting as hypercalcemia, hyperphosphatemia, suppressed PTH, and hypercalciuria 4

The American Journal of Kidney Diseases and Praxis Medical Insights recommend assessing anticoagulation status before considering any vitamin K supplementation, and never supplementing vitamin K in patients on warfarin 1, 2
Praxis Medical Insights suggests measuring baseline 25(OH)D level and initiating loading dose 50,000 IU weekly × 8-12 weeks for deficiency, and adding 1,000-2,000 IU daily for insufficiency 3, 4