What loading and maintenance doses of liposomal vitamin D3 (cholecalciferol) and vitamin K2 should be used for a patient with a 25‑hydroxyvitamin D level of 28 ng/mL who is currently taking 1,000 IU vitamin D3 and 90 µg vitamin K daily?

Vitamin D3/K2 Dosing for Level of 28 ng/mL

For a vitamin D level of 28 ng/mL (just below target), treat with 50,000 IU vitamin D3 weekly for 8 weeks to achieve levels above 30 ng/mL, then maintain with 1,500-2,000 IU daily. Your current dose of 1,000 IU daily is insufficient, as evidenced by your suboptimal level despite consistent use 1.

Loading Phase (8 Weeks)

Vitamin D3: 50,000 IU once weekly for 8 weeks (total 400,000 IU) 1

• This is the Endocrine Society's standard loading protocol for vitamin D deficiency in adults
• Alternative: 6,000 IU daily for 8 weeks if you prefer daily dosing 1
• Take with food to enhance absorption 2
• Liposomal formulation may improve bioavailability, though standard formulations are well-validated in guidelines

Vitamin K2: Continue 90 mcg daily during loading phase

• Your current K2 dose is adequate for supporting vitamin D metabolism
• No loading dose needed for vitamin K2
• Vitamin K supplementation helps prevent potential hypercalcemia during high-dose vitamin D therapy 3

Maintenance Phase (After 8 Weeks)

Vitamin D3: 1,500-2,000 IU daily 1

• Your previous 1,000 IU daily was insufficient to maintain levels above 30 ng/mL
• Research confirms 2,000 IU daily maintains levels in the recommended range even after breaks in supplementation 4, 5
• One study showed 2,000 IU daily dropped levels back to 20 ng/mL after 3 months, suggesting some individuals may need higher maintenance 4

Vitamin K2: Continue 90 mcg daily

• Adequate for long-term bone health support
• No dose adjustment needed

Critical Monitoring Points

• Recheck 25(OH)D level 3-4 months after starting loading dose to confirm achievement of target >30 ng/mL 3
• If level remains <30 ng/mL after loading, consider:
  • Obesity (requires 2-3x higher doses: 6,000-10,000 IU daily) 1
  • Malabsorption (celiac disease, cystic fibrosis) 1
  • Medication interactions (anticonvulsants, glucocorticoids) 1

Safety Considerations

No calcium monitoring needed unless you have:

• Primary hyperparathyroidism 1
• Granulomatous disorders (sarcoidosis, tuberculosis) 1
• History of kidney stones

The 50,000 IU weekly protocol is safe:

• No increased risk of hypercalcemia or hypercalciuria at these doses 6, 7
• Upper tolerable limit is 10,000 IU daily for adults (your weekly dose averages 7,143 IU/day) 1
• Avoid single massive doses (>300,000 IU at once), which paradoxically increase fall risk 3

Why Your Current Regimen Failed

Your 1,000 IU daily dose is below the 1,500-2,000 IU needed to maintain levels above 30 ng/mL 1. Research demonstrates that 2,000 IU daily is the minimum effective maintenance dose for most adults 4, 5, 8. At 28 ng/mL, you're in vitamin D insufficiency, requiring active correction rather than simple maintenance.

Liposomal Formulation Note

While liposomal delivery may theoretically enhance absorption, all guideline-based dosing recommendations use standard oil-based vitamin D3 formulations 1, 2. If using liposomal drops, follow the same IU dosing—the delivery system shouldn't require dose adjustment unless you have documented malabsorption.