About Vitamin K1

Vitamin K1 (phylloquinone) is the primary dietary form of vitamin K that excels at its fundamental role in blood coagulation with unmatched clinical evidence.

Effectiveness Scores

Blood Health Support: 10.0/10 (moderate evidence).
Vitamin K1 plays a necessary role in normal blood clotting. It helps activate several clotting proteins allowing them to bind calcium and function correctly. When vitamin K1 intake is too low, clot formation becomes less efficient, which increases the risk of excessive or prolonged bleeding.
Why this rating: The role of vitamin K1 in coagulation is firmly established. Its mechanisms are well understood, it is routinely used in clinical care, and deficiencies produce clear, predictable effects. Few nutrient functions are as consistently supported across biochemistry, clinical research, and medical practice, which justifies a very high level of confidence.
Bone Health: 4.0/10 (moderate evidence).
Vitamin K1 helps activate proteins in bone tissue that are important for binding calcium and maintaining proper bone structure. This process supports bone mineralization and helps regulate calcium balance. Higher dietary intake of K1 has been linked in some studies to slightly better bone density, though the evidence is inconsistent.
Why this rating: Although vitamin K1 plays a biochemical role in bone metabolism, its clinical impact on bone density or fracture prevention is weak. Results from human trials are inconsistent and often show minimal effects. K1 also tends to remain in the liver rather than reaching bone tissue effectively, which may explain its limited benefit compared to K2. Overall, evidence supports a biological rationale but lacks convincing proof of meaningful bone health improvements.
Cardiovascular Health: 3.0/10 (moderate evidence).
Vitamin K1 helps activate a compound that prevents calcium from depositing in blood vessel walls. In theory, this process could protect arteries from stiffening and reduce the risk of atherosclerosis. However, for K1 to have this effect, it must reach vascular tissues in sufficient amounts to activate MGP, which may not occur efficiently since most K1 remains stored in the liver.
Why this rating: While the underlying mechanism is scientifically plausible, human studies haven't shown convincing cardiovascular benefits from vitamin K1 supplementation. Its limited availability to vascular tissues likely reduces effectiveness. Most positive findings in this area involve K2, not K1. Overall, the evidence for K1's role in heart and vascular health remains weak and largely theoretical.

Dosage & Timeline

Standard Dosages

Adequate Intake:
- Adults:
  - Men: 120 mcg/day
  - Women: 90 mcg/day
- Adolescents 14-18 years: 75 mcg/day
- Children 9-13 years: 60 mcg/day
Supplemental Dosages: 100 mcg/day

Timeline to See Results

All outcomes may be noticed after extended use or lack enough studies to establish an effectiveness timeline.

Safety Information

Pregnancy and breastfeeding: Vitamin K1 is considered safe during pregnancy and breastfeeding, as it is crucial for fetal development and blood coagulation. The recommended dietary allowance (RDA) for pregnant women is 90 mcg/day for women aged 19 years and older, and for breastfeeding women, it's 90 mcg/day.
Drug interactions: Vitamin K1 can interfere with blood-thinning medications (e.g., warfarin, coumadin), as it helps in the clotting process. People on anticoagulants should be consistent in their vitamin K intake and avoid large fluctuations, as it could counteract the effects of the medication. It's crucial for individuals taking these medications to consult a healthcare provider before supplementing with vitamin K.
Chronic kidney disease: People with kidney disease or impaired kidney function should consult a healthcare provider before taking vitamin K supplements, especially synthetic forms, due to the potential for altered vitamin K metabolism.

Side Effects

Common side effects:

Vitamin K from food sources typically does not cause side effects.
In rare cases, supplements may cause gastrointestinal distress (e.g., upset stomach, diarrhea).

Rare side effects:

Allergic reactions: Skin rash, itching, or swelling.
Vitamin K toxicity: Generally, vitamin K toxicity is not a concern when consumed through food sources. However, very high doses from supplements (particularly synthetic forms) may increase the risk of adverse effects, particularly in individuals on anticoagulant therapy (like warfarin).

Usage Information

Vitamin K is primarily intended to support blood clotting and cardiovascular health.

User Experience

User experiences with vitamin K1 supplementation are generally minimal, reflecting that most individuals obtain sufficient amounts from leafy green vegetables. Oral K1 is well-tolerated, with few reported side effects, and is most effectively absorbed when taken with a fat-containing meal. Users rarely notice immediate effects, as vitamin K1 primarily acts on coagulation and bone metabolism behind the scenes.

Supplementation is mainly relevant for specific populations: newborns (universal IM prophylaxis), individuals with malabsorption conditions (Crohn’s, celiac, cystic fibrosis), those on long-term antibiotics, and patients on warfarin, who must maintain consistent intake to avoid INR fluctuations. While K1 remains the standard for coagulation and deficiency management, users seeking cardiovascular or bone health benefits often prefer K2 (MK-7) due to its longer half-life and better tissue distribution. Oral forms are highly tolerated, while IM injections cause local discomfort and are reserved for clinical contexts.

Alternative Names

Phylloquinone

Vitamin K1