Positives

• One ME/CFS patient reported that vitamin K2 supplementation produced an increase in energy and the ability to exercise longer with less post-exertional malaise, which she described as her “greatest result so far” from a single supplement Phoenix Rising.
  
  
• A user reported improvements in dental and vascular health including stopped gum bleeding, fewer bruises from minor injuries, and noticeably less dental plaque, consistent with K2’s known role in calcium metabolism Phoenix Rising.
  
  

Negatives

• Patients on warfarin or Coumadin commonly see vitamin K2 directly counteract their anticoagulant, with even small MK-7 doses (10-20 mcg/day) lowering INR in 4 out of 10 subjects, raising clot risk. Drugs.com.
• Cleveland Clinic emphasizes that all forms of vitamin K, including K2 MK-4 and MK-7, can dangerously interfere with warfarin and require careful coordination; patients on warfarin should not start vitamin K2 without their anticoagulation clinic's approval. Cleveland Clinic.
• ConsumerLab notes that DOACs like apixaban, rivaroxaban, and dabigatran are not affected by vitamin K, but warfarin patients should avoid even small doses of K2; there is no robust evidence K2 improves Long COVID-specific outcomes to justify the interaction risk. ConsumerLab.

Hurdles & Side Effects

• Forum members note that vitamin K2 should generally not be supplemented while vitamin D is markedly deficient, because the interaction can drive calcium mobilization inappropriately; they also note that most commercial MK-7 products contain only 100 mcg while the dose at which K2-dependent proteins are fully activated is closer to 200 mcg, explaining some null results Phoenix Rising.