Vitamin K (Phylloquinone)
Useful mainly for preventing/treating vitamin K deficiency bleeding and reversing warfarin.
Quick decision guide
May help most
preventing/treating vitamin K deficiency bleeding and reversing warfarin
Common dosing range
AI 120 mcg/day (men) and 90 mcg/day (women); supplements 50–500 mcg
When to expect effects
Hours to days for clotting; months for bone/vascular endpoints
Watch out for
Potent interaction with warfarin; keep intake consistent
What is it
Phylloquinone (vitamin K1, phytonadione) is the major dietary form of vitamin K, found primarily in green leafy vegetables. It is a fat-soluble vitamin essential for blood clotting and bone metabolism through activation of specific vitamin K-dependent proteins.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
vitamin k deficiency bleeding (newborns and infants) Strong Evidence | Prevents a serious bleeding disorder | newborns and infants (routine prophylaxis) | Hours to days |
warfarin reversal Strong Evidence | Restores coagulation | patients with elevated INR or bleeding on vitamin K antagonists, under clinical management | Hours to days |
hemorrhagic disease in malabsorption Strong Evidence | Corrects deficiency-related bleeding | people with fat malabsorption (biliary obstruction, cystic fibrosis, etc.) | Hours to days |
bone density and fracture prevention Limited Evidence | Small/inconsistent | not clearly established for K1 specifically | Months |
vitamin k deficiency bleeding (newborns and infants)
- Effect
- Prevents a serious bleeding disorder
- Best fit
- newborns and infants (routine prophylaxis)
- Time
- Hours to days
warfarin reversal
- Effect
- Restores coagulation
- Best fit
- patients with elevated INR or bleeding on vitamin K antagonists, under clinical management
- Time
- Hours to days
hemorrhagic disease in malabsorption
- Effect
- Corrects deficiency-related bleeding
- Best fit
- people with fat malabsorption (biliary obstruction, cystic fibrosis, etc.)
- Time
- Hours to days
bone density and fracture prevention
- Effect
- Small/inconsistent
- Best fit
- not clearly established for K1 specifically
- Time
- Months
Evidence for 4 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
vitamin k deficiency bleeding (newborns and infants)
Corrects deficiencyPhylloquinone is a required cofactor for carboxylation of clotting factors II, VII, IX, and X, and newborns are born with low stores. Routine K1 administration prevents vitamin K deficiency bleeding (hemorrhagic disease of the newborn), an established standard of care. This is a well-validated clinical use.
Bottom line: Routine newborn vitamin K1 reliably prevents a dangerous bleeding disorder.
warfarin reversal
Disease adjunctVitamin K1 directly antagonizes warfarin by replenishing the cofactor for clotting-factor carboxylation, and it is standard therapy for warfarin-related over-anticoagulation and bleeding. Dose and route are chosen by clinicians based on INR and bleeding severity. This is a well-established medical use.
Bottom line: Vitamin K1 is the standard antidote for warfarin over-anticoagulation.
hemorrhagic disease in malabsorption
Corrects deficiencyBecause phylloquinone is fat-soluble, conditions causing fat malabsorption can produce vitamin K deficiency and bleeding. Repletion, sometimes by non-oral routes, corrects the coagulopathy. This is an accepted deficiency-correction use.
Bottom line: Vitamin K1 corrects bleeding from deficiency in fat-malabsorption states.
bone density and fracture prevention
Biomarker supportVitamin K-dependent osteocalcin requires carboxylation to bind bone mineral, providing a rationale for bone benefit, and K1 supplementation can reduce undercarboxylated osteocalcin. Trials of K1 for fracture prevention are inconsistent and largely surrogate-focused. The effect is on a bone biomarker rather than proven fracture reduction.
Bottom line: K1 improves a bone-protein biomarker, but fracture-prevention evidence is weak and mixed.
Evidence is mixed
Biomarker effects on osteocalcin are consistent, but clinical fracture-prevention trials for K1 are inconsistent.
How it works
How to take it
What to track
2 commercial forms
Compare the main delivery options and what they’re best suited for.
Phylloquinone (vitamin K1)
Found in green leafy vegetables. The standard form used for warfarin reversal and routine supplementation.
The natural plant form; absorption improves substantially with dietary fat.
Phytonadione (synthetic K1)
The prescription form used in hospitals for anticoagulant reversal and newborn prophylaxis.
Chemically identical to natural K1; available in oral, IV, and IM forms.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Who should avoid it
- patients on warfarin should not change K intake without prescriber coordination
Pregnancy & breastfeeding
Phylloquinone is considered safe in normal dietary and supplemental amounts; newborns routinely receive K1 prophylaxis.
Interactions
K1 directly antagonizes these anticoagulants; inconsistent intake can shift INR dangerously
Can lower vitamin K absorption and status
No significant interaction with direct oral anticoagulants
Food sources
| Food | Amount | %DV |
|---|---|---|
| Kale (1 cup, raw) | 472 mcg | — |
| Collard greens (1/2 cup, cooked) | 530 mcg | — |
| Spinach (1/2 cup, cooked) | 444 mcg | — |
| Broccoli (1/2 cup, cooked) | 110 mcg | — |
| Brussels sprouts (1/2 cup, cooked) | 150 mcg | — |
| Romaine lettuce (1 cup) | 48 mcg | — |
| Soybean oil (1 tbsp) | 25 mcg | — |
| Canola oil (1 tbsp) | 10 mcg | — |
Kale (1 cup, raw)
- Amount
- 472 mcg
- %DV
- —
Collard greens (1/2 cup, cooked)
- Amount
- 530 mcg
- %DV
- —
Spinach (1/2 cup, cooked)
- Amount
- 444 mcg
- %DV
- —
Broccoli (1/2 cup, cooked)
- Amount
- 110 mcg
- %DV
- —
Brussels sprouts (1/2 cup, cooked)
- Amount
- 150 mcg
- %DV
- —
Romaine lettuce (1 cup)
- Amount
- 48 mcg
- %DV
- —
Soybean oil (1 tbsp)
- Amount
- 25 mcg
- %DV
- —
Canola oil (1 tbsp)
- Amount
- 10 mcg
- %DV
- —
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
What's the difference between vitamin K1 and K2?⌄
K1 (phylloquinone) is the plant form, used mainly by the liver for blood clotting. K2 (menaquinones) is bacterial and animal-derived, with greater activity in bone and vascular tissue. Both contribute to vitamin K status but have different tissue preferences.
Can I take K1 if I'm on warfarin?⌄
Only with your prescriber's coordination. K1 directly antagonizes warfarin and can dangerously lower your INR if added or stopped suddenly. The key is consistency in K intake from all sources.
Do I need a K1 supplement if I eat greens?⌄
Most likely not. A serving or two of leafy greens per day usually provides more than the AI. Supplementation matters most in malabsorption, restricted diets, or specific clinical indications.
Why do babies get a vitamin K shot at birth?⌄
Newborns are born with very low vitamin K stores and limited intestinal flora, putting them at risk of potentially fatal hemorrhagic disease of the newborn. A single K1 injection reliably prevents this.
Does K1 help bones?⌄
There is some observational evidence linking higher K1 intake with better bone density, but trial evidence is mixed. K2 (particularly MK-7) shows more consistent bone-specific effects.
References by claim
Track Vitamin K (Phylloquinone) with Pilora
Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.
Coming to App StoreDisclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.