Vitamin K1, the plant form of vitamin K from leafy greens, reliably supports normal blood clotting — a role backed by strong evidence. Its longer-life, stronger-bone, and healthier-artery signals remain promising but unproven. It is inexpensive, very safe taken by mouth, and easy to get from food. The main caution is steady, coordinated intake for anyone on warfarin-type blood thinners. (Full Review)

Protocol

Dose

500 µg–1 mg/day

Common optimization range; dietary adequacy ~90–120 µg/day; up to 5 mg/day in bone trials

With Food

Largest fatty meal

Fat and bile needed for absorption; clock time unimportant

Frequency

Once daily

Short half-life; no need to split doses for K1

Time to effect

Blood Clotting

Hours to days

Clotting proteins restored to full activity

Activation Markers

Days to weeks

Carboxylated osteocalcin and dp-ucMGP shift

Bone & Artery Outcomes

Months to years

Bone density, calcification, and clinical outcomes

Benefits

High: Normal blood clotting and prevention of deficiency bleeding

Medium: Improved activation of bone and vascular proteins

Low: Lower risk of death from any cause; reduced fracture risk; slowed arterial and coronary calcification; lower atherosclerotic cardiovascular disease risk

Speculative: Improved insulin sensitivity and glucose handling; support of cognitive function in aging

Contraindications

Known hypersensitivity to injectable phytonadione

Key Interactions

Warfarin and other vitamin K antagonists (warfarin, acenocoumarol, phenprocoumon)

Fat-absorption–blocking drugs (orlistat, cholestyramine, colesevelam, mineral oil)

Broad-spectrum antibiotics (cephalosporins, fluoroquinolones, metronidazole)

High-dose vitamin E (>800 IU/day)

Risk & Side Effects

High: Antagonism of warfarin and other vitamin K antagonists

Medium: Severe reactions to intravenous phytonadione

Low: Gastrointestinal discomfort; injection-site and delayed skin reactions

Speculative: Theoretical excess-clotting risk in people not on blood thinners

Monitoring

Marker	Target	Why
Prothrombin time / INR	~0.8–1.1 (not anticoagulated)	Confirms clotting is normal and detects deficiency or drug effect
dp-ucMGP	<400–500 pmol/L	Functional marker of how well vitamin K is activating the artery-protective protein
Undercarboxylated osteocalcin (%ucOC)	Lower is better	Reflects vitamin K availability for bone protein activation
PIVKA-II	Undetectable / very low	Most sensitive marker of subclinical vitamin K deficiency
Plasma phylloquinone	Above ~1.0 nmol/L	Directly reflects recent K1 intake and status

Cadence: INR tied to any intake change (e.g., weekly until stable) for anticoagulated users; functional markers such as dp-ucMGP every 6–12 months for those targeting calcification or bone

Qualitative Assessment

Absence of easy bruising, bleeding gums, or frequent nosebleeds
Stable, in-range clotting control for those on anticoagulants
Maintained bone density and stable vascular calcification scores over the long term

Vitamin K1 for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment