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Clear vitamin K1 softgels beside dark green kale leaves
DoseRoutine Vitamin K1 — Clear vitamin K1 softgels beside dark green kale leaves. Original DoseRoutine photography.
vitaminInjectableOTC supplementVitamin K1 (phytonadione) is available both as an FDA-approved prescription injectable/oral product for anticoagulation reversal and as an over-the-counter dietary supplement at nutritional dosesTherapeutic reversal doses used in the cited trial are far higher than routine dietary-supplement doses and were administered under clinical supervision

Vitamin K1Benefits, Dosage & Interactions

Also known as: Phytonadione, Phylloquinone

Vitamin K1, also known as phytonadione or phylloquinone, is a fat-soluble vitamin essential for several bodily functions, most notably blood clotting. It is naturally found in many green leafy vegetables and is the primary dietary form of Vitamin K. Research on Vitamin K1 focuses on healthy aging.

How much Vitamin K1 do people take?

Oral doses of roughly 1–5 mg were used in the Baker et al. randomized trial to reverse asymptomatic over-anticoagulation in warfarin patients; dietary reference intake for healthy adults is on the order of 90–120 mcg/day, distinct from these therapeutic doses. Route reported: Oral in the cited reversal trial; also available as an injectable (phytonadione) for clinical use. Frequency reported: Single oral dose in the reversal-of-anticoagulation study cited here. These are amounts documented in the cited studies and labels for Vitamin K1 — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.

See the full reported protocol and its sources

Researched by DoseRoutine Research TeamReviewed for accuracy by Nicholas Alexander, RSE, SO, PMPLast updated Educational reference only — not medical advice. Always confirm dosing and safety decisions with a licensed clinician.

Evidence: Moderate — One published human randomized trial; results not yet replicated.
Evidence strengthModerate · 3/4
PreclinicalStrong human evidence

One published human randomized trial; results not yet replicated.

Chemical structure of Vitamin K1 (PubChem CID 5284607)
Structure via PubChem
Whole-body biological half-life
Not applicable
Typical timing
with a meal
Food rule
with food
Default unit
mcg

What published protocols report

Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.

Reported amounts
Oral doses of roughly 1–5 mg were used in the Baker et al. randomized trial to reverse asymptomatic over-anticoagulation in warfarin patients; dietary reference intake for healthy adults is on the order of 90–120 mcg/day, distinct from these therapeutic doses[1][2]
Route studied
Oral in the cited reversal trial; also available as an injectable (phytonadione) for clinical use[1][2]
Frequency
Single oral dose in the reversal-of-anticoagulation study cited here[1][2]
Half-life
Reported on the order of a few hours in circulation, consistent with its role as a rapidly acting coagulation factor precursor[1][2]

Reported for Vitamin K1 in the cited sources. Published ranges are not dosing advice.

Mixing Vitamin K1: bacteriostatic water and syringe units

The vial arrives as dry powder. How much water you add sets the strength, and the strength sets the mark you draw to on the syringe. The table assumes a 5 mg vial and a 250 mcg example draw on a U-100 insulin syringe, where 100 units is one millilitre. If your vial is a different size, scale it — the arithmetic is the same.

Bacteriostatic water addedResulting strength250 mcg draws to
1 mL5 mg/mL5 units
2 mL2.5 mg/mL10 units
3 mL1.67 mg/mL15 units

Units, not millilitres. Insulin syringes are marked in units, and mixing up mcg and mg on a peptide label is the single most common error people report. Check the label twice. Run your own vial through the calculator.

Storage and stability

Before mixing
Sealed and still as a dry powder, Vitamin K1 vials are normally kept in the fridge at 2–8 °C, out of light. Short spells at room temperature during shipping are the norm for lyophilized peptides and are not, on their own, a sign the vial is spoiled.
After mixing
Once bacteriostatic water goes in, the vial belongs in the fridge and is generally treated as good for about 28 days — that is how long the benzyl alcohol in bacteriostatic water is relied on to hold back bacterial growth. Plain sterile water has no preservative, so a vial mixed with it is a single-session vial. Never freeze a reconstituted vial.
When to throw it out
A properly mixed vial is clear. Cloudiness, floating strands, a color change or powder that will not go into solution after gentle swirling all mean the vial should be discarded rather than used. Shaking a peptide vial hard is the usual cause — swirl it, or run the water down the inside wall of the vial instead of onto the powder.

Handling and shelf-life figures describe general practice for lyophilized peptides. They are not a dose and not medical advice — your prescriber or the product label sets the amount.

References & evidence

Documents the Vitamin K1 entry is written from. Each number matches an inline marker above.

  1. [1]Phylloquinone (Vitamin K1): Occurrence, Biosynthesis and FunctionsBasset GJ, Latimer S, Fatihi A, Soubeyrand E, Block A · Mini Reviews in Medicinal Chemistry · 2017 · Peer-reviewed · PMID 27337968
  2. [2]Reversal of asymptomatic over-anticoagulation by orally administered vitamin KBaker P, Gleghorn A, Tripp T, Paddon K, Eagleton H, Keeling D · British Journal of Haematology · 2006 · Peer-reviewed · PMID 16643436

References & Evidence

Sources on this page that document Vitamin K1 dosing, timing and safety.

  1. [1]National Center for Biotechnology Information View source

Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.

What is Vitamin K1 studied for?

Longevity

Deficiency-driven — not a performance booster

Vitamins primarily help when you're actually low. Extra doses on top of normal levels rarely add strength, endurance, or fat loss, and some fat-soluble vitamins (A, D, E, K) can build up to harmful levels.

  • Confirm a deficiency with bloodwork before supplementing long-term (e.g. 25(OH)D for vitamin D, B12/folate, ferritin, magnesium RBC).
  • Talk to your doctor or a registered dietitian about the right dose for your labs, medications, and conditions — especially in pregnancy, kidney/liver disease, or while on blood thinners.
  • Re-test every 3–6 months and stop or lower the dose once levels are in range.

Educational information only — not medical advice. See our AI & medical policy.

What is Vitamin K1?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.

Vitamin K1, also known as phytonadione or phylloquinone, is a fat-soluble vitamin essential for several bodily functions, most notably blood clotting. It is naturally found in many green leafy vegetables and is the primary dietary form of Vitamin K. Vitamin K refers to a group of structurally similar fat-soluble vitamins, with K1 and K2 being the most common. Vitamin K1 plays a crucial role as a coenzyme for a specific class of proteins known as gla-proteins (gamma-carboxyglutamic acid proteins). These proteins are involved in various physiological processes, including hemostasis (blood clotting) and bone metabolism. The human body obtains Vitamin K1 primarily through diet, and to a lesser extent, from bacterial synthesis of Vitamin K2 in the gut. Deficiencies in Vitamin K1 can lead to impaired blood coagulation, potentially resulting in excessive bleeding. (NIH ODS, PubChem)

What does the research say about Vitamin K1?

Tap a section to expand.

Vitamin K1 functions as a cofactor for the enzyme gamma-glutamyl carboxylase. This enzyme is responsible for the post-translational carboxylation of specific glutamic acid residues in certain proteins, converting them into gamma-carboxyglutamic acid (Gla) residues. This carboxylation step is critical as it enables these Gla proteins to bind calcium ions, which is an essential step in their activation. Key Gla proteins involved in blood coagulation include prothrombin (Factor II), Factor VII, Factor IX, and Factor X, as well as protein C, protein S, and protein Z, which regulate coagulation. Without adequate Vitamin K1, these clotting factors cannot be fully activated, impairing the body's ability to form clots. (NIH ODS, DrugBank) The absorption of Vitamin K1 is dependent on dietary fat and bile salts, as it is a fat-soluble vitamin. It is primarily absorbed in the small intestine and then transported to the liver via chylomicrons. In the liver, Vitamin K1 enters the Vitamin K cycle, a metabolic pathway that regenerates the active form of Vitamin K from its inactive epoxide form. This recycling mechanism allows a relatively small amount of Vitamin K to be used repeatedly. (PubChem)

Source for this section: Sources for How does Vitamin K1 work?: Jumps to this entry in the sources and references list at the end of the page.

The primary benefits of adequate Vitamin K1 intake revolve around its role in: * **Blood Coagulation:** Vitamin K1 is indispensable for the synthesis and activation of several blood clotting factors. Adequate levels help ensure proper hemostasis, preventing excessive bleeding from injuries or other conditions. (NIH ODS, MedlinePlus) * **Bone Health:** While Vitamin K2 is more widely recognized for its direct impact on bone mineralization, Vitamin K1 also plays a role. It is a cofactor for the carboxylation of osteocalcin, a protein produced by osteoblasts (bone-forming cells). Carboxylated osteocalcin is essential for binding calcium and integrating it into the bone matrix, contributing to bone strength and density. (Examine.com) * **Cardiovascular Health:** Some research suggests a potential role for Vitamin K1 in maintaining cardiovascular health, though this area is more often associated with Vitamin K2. Vitamin K-dependent proteins, such as Matrix Gla Protein (MGP), when carboxylated by Vitamin K, inhibit arterial calcification. While K2 is more potent in this regard, K1 may also contribute to the overall Vitamin K status that influences this process. (Cochrane Library review findings cited by other sources)

The role of Vitamin K1 in blood coagulation is highly established and supported by extensive evidence. Its necessity is demonstrated by the effectiveness of Vitamin K1 supplementation in reversing anticoagulant effects of Vitamin K antagonists like warfarin, and in treating Vitamin K deficiency bleeding in infants. Clinical guidelines from major medical organizations universally recognize Vitamin K1's role in hemostasis. (FDA product labels, MedlinePlus) Evidence for Vitamin K1's direct benefits on bone health is emerging, with studies often focusing on its combined effect with Vitamin D or comparing it to Vitamin K2. While Vitamin K2 receives more attention for bone mineral density and fracture risk, Vitamin K1 also contributes to the carboxylation of osteocalcin. Observational studies have linked higher dietary Vitamin K1 intake with better bone health markers, but randomized controlled trials specifically isolating K1's effect on bone outcomes are less common than for K2. (NIH ODS, Examine.com) The evidence for Vitamin K1's direct impact on cardiovascular health is weaker than for Vitamin K2. While Vitamin K-dependent proteins like MGP are crucial for preventing arterial calcification, and K1 is essential for their carboxylation, K2 appears to be more effective in activating these proteins in peripheral tissues. Research often aggregates dietary Vitamin K intake, making it challenging to isolate the specific contributions of K1 versus K2 to cardiovascular outcomes. (Cochrane Library reviews on Vitamin K and cardiovascular health)

Vitamin K1 is generally considered safe when taken orally at appropriate levels. Adverse effects from dietary intake are rare, even at high amounts. When administered as an injection, particularly intravenously, some individuals may experience serious reactions, including flushing, dizziness, rapid heart rate, low blood pressure, difficulty breathing, and allergic reactions. However, these are uncommon with oral supplementation. In rare cases, liver enzyme elevations or skin reactions have been reported with certain forms or routes of administration. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.

Individuals with certain medical conditions should exercise caution or avoid Vitamin K1 supplementation unless directed by a healthcare professional. Persons who have had an allergic reaction to Vitamin K1 previously should not use it. Those with a genetic condition called G6PD deficiency may be at risk for hemolytic anemia if given large doses of Vitamin K. Newborn infants are routinely given Vitamin K1 to prevent Vitamin K deficiency bleeding, but specific formulations and doses are used under medical supervision. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.

Vitamin K1 is contraindicated in individuals with a known hypersensitivity or allergic reaction to phytonadione or any components of its formulations. It should not be used in patients with severe liver disease who have impaired bile secretion, as this can hinder its absorption. It is also generally avoided in patients undergoing dialysis, unless specifically indicated and monitored by a clinician due to potential interactions and underlying conditions. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.

Vitamin K1 can significantly interact with certain medications. The most notable interaction is with **warfarin (Coumadin®)** and other oral anticoagulants (blood thinners) that work by antagonizing Vitamin K. Vitamin K1 directly counteracts the effects of these medications, reducing their effectiveness and increasing the risk of blood clot formation. Individuals taking warfarin must maintain a consistent dietary intake of Vitamin K1 and should not take supplements without strict medical supervision. **Orlistat (Xenical®, Alli®)**, a medication used for weight loss, inhibits the absorption of dietary fats and can therefore reduce the absorption of fat-soluble vitamins, including Vitamin K1. **Cholestyramine (Prevalite®, Questran®)** and **colestipol (Colestid®)**, bile acid sequestrants used to lower cholesterol, can bind to fat and bile acids in the gut, thereby reducing the absorption of fat-soluble vitamins. **Mineral oil**, when used as a laxative, can also interfere with the absorption of fat-soluble vitamins by dissolving them and preventing their uptake. **Excessive intake of Vitamin E** through supplements may theoretically interfere with Vitamin K activity and increase the risk of bleeding, though this is primarily observed with very high doses of Vitamin E. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.

Vitamin K1 is a fat-soluble vitamin, meaning it is best absorbed when consumed with dietary fat. Therefore, it is typically recommended to take Vitamin K1 supplements with a meal that contains some fat to maximize absorption. The half-life is approximately 2 hours, but its biological effects, particularly on clotting factor synthesis, can last longer due to its role in the Vitamin K cycle. There is no specific time of day that is universally better for taking Vitamin K1, but consistency, especially in its interaction with other medications like warfarin, is crucial.

Source for this section: Sources for When should you take Vitamin K1?: Jumps to this entry in the sources and references list at the end of the page.

Put it into practice

Reading about Vitamin K1 is the first step — DoseRoutine helps you act on it. These free tools turn what you just learned into a routine.

What interacts with Vitamin K1?

Documented interactions for Vitamin K1: the other compound, the severity and confidence of the interaction, what happens, and what to do.
Interacts withSeverityTypeWhat happensWhat to do
Any vitamin + medicationNoteCategory ruleConfidence: theoreticalCertain vitamins interact with specific medications (e.g., vitamin K with blood thinners).Source pendingSpecific pairs are checked against a licensed source; confirm with your provider.
WarfarinCautionCompound pairConfidence: theoreticalVitamin K reverses vitamin K antagonist activity and shifts INR.Source pendingKeep vitamin K intake consistent; do not start or stop supplementation without INR monitoring.
Any + CautionCategory ruleConfidence: theoreticalVitamin K reverses vitamin K antagonist activity and shifts INR.Source pendingKeep vitamin K intake consistent; do not start or stop supplementation without INR monitoring.
ApixabanCautionCompound pairConfidence: theoreticalVitamin K reverses vitamin K antagonist activity and shifts INR.Source pendingKeep vitamin K intake consistent; do not start or stop supplementation without INR monitoring.
RivaroxabanCautionCompound pairConfidence: theoreticalVitamin K reverses vitamin K antagonist activity and shifts INR.Source pendingKeep vitamin K intake consistent; do not start or stop supplementation without INR monitoring.
DabigatranCautionCompound pairConfidence: theoreticalVitamin K reverses vitamin K antagonist activity and shifts INR.Source pendingKeep vitamin K intake consistent; do not start or stop supplementation without INR monitoring.
ClopidogrelCautionCompound pairConfidence: theoreticalVitamin K reverses vitamin K antagonist activity and shifts INR.Source pendingKeep vitamin K intake consistent; do not start or stop supplementation without INR monitoring.

Frequently asked questions about Vitamin K1

Vitamin K1 (phytonadione or phylloquinone) is one type of Vitamin K. Vitamin K is a group of fat-soluble vitamins, with K1 and K2 (menaquinone) being the most common forms. They have similar functions but also some distinct roles in the body.

Excellent dietary sources of Vitamin K1 include green leafy vegetables such as kale, spinach, collard greens, turnip greens, broccoli, and Brussels sprouts. Other sources include some vegetable oils like soybean and canola oil.

Vitamin K1 is essential for normal blood clotting, but it does not typically cause inappropriate blood clots or hypercoagulation in healthy individuals. Its role is to ensure the proper function of the natural clotting cascade. However, in individuals taking blood-thinning medications like warfarin, sudden increases in Vitamin K1 intake can counteract the medication's effects, potentially leading to an increased risk of clotting.

Both K1 and K2 are Vitamin K, but they have different chemical structures and absorption pathways. K1 is primarily involved in blood clotting in the liver. K2, especially its longer-chain forms, is more involved in calcium metabolism in soft tissues like arteries and bones.

Vitamin K1 is a vitamin, and interactions are possible with prescriptions, hormones, peptides and other supplements in the same routine. Because Vitamin K1 is usually taken with a meal, most avoidable conflicts come from what else lands in that same window. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers Vitamin K1 with no sign-up.

Vitamin K1 is typically taken with a meal. Published protocols usually have it taken with food. Ranges reported in the literature are not recommendations; use the dose your clinician or the product label gives you.

Combining a vitamin like Vitamin K1 with TRT is usually a question of labs rather than a blanket yes or no: the ester, injection interval and any aromatase inhibitor all change the answer. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions

Each peptide class carries its own profile against Vitamin K1: a healing peptide raises different questions than a GLP-1 agonist or a growth-hormone secretagogue. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.

Published frequency for Vitamin K1 varies by protocol and formulation, so the label or prescription is what sets it. It is typically taken with a meal. Most protocols have it taken with food. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps

The effect of a missed dose of Vitamin K1 depends on the protocol and formulation you are on. Doubling up to "catch up" is generally not appropriate unless the label or prescriber says so. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.

For Vitamin K1 the useful record is the dose, the time it was actually taken, and what else was taken in the same window. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.

Oral doses of roughly 1–5 mg were used in the Baker et al. randomized trial to reverse asymptomatic over-anticoagulation in warfarin patients; dietary reference intake for healthy adults is on the order of 90–120 mcg/day, distinct from these therapeutic doses. Route reported: Oral in the cited reversal trial; also available as an injectable (phytonadione) for clinical use. Frequency reported: Single oral dose in the reversal-of-anticoagulation study cited here. These are amounts documented in the cited studies and labels for Vitamin K1 — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.

Which studies looked at Vitamin K1?

Peer-reviewed research indexed in PubMed. Each entry links to the original record.

  1. 1.Vitamin K: Double Bonds beyond Coagulation Insights into Differences between Vitamin K1 and K2 in Health and Disease(opens PubMed in a new tab)Int J Mol Sci · 2019 · PMID 30791399 · https://pubmed.ncbi.nlm.nih.gov/30791399/

Sources cited on this page

Specific documents referenced by the numbered markers above. Each number matches the marker in the text.

  1. PubChem CID 5284607(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/5284607

Verify at

Publisher search links for Vitamin K1. These are places to check the information — they are not citations, so they are not numbered.

DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.

What is the short answer on Vitamin K1?

Plain-text summary, safe to quote verbatim:

Vitamin K1, also known as phytonadione or phylloquinone, is a fat-soluble vitamin essential for several bodily functions, most notably blood clotting. It is naturally found in many green leafy vegetables and is the primary dietary form of Vitamin K. Research on Vitamin K1 focuses on healthy aging.
Source: DoseRoutine — https://doseroutine.com/library/vitamin-k1

Vitamin K1 cheat sheet

DoseRoutine cheat sheet · Vitamin

Vitamin K1

Vitamin K1, also known as phytonadione or phylloquinone, is a fat-soluble vitamin essential for several bodily functions, most notably blood clotting. It is naturally found in many green leafy vegetables and is the primary dietary form of Vitamin K.

Evidence

Moderate

One published human randomized trial; results not yet replicated.

Studied range

Oral doses of roughly 1–5 mg were used in the Baker et al. randomized trial to reverse asymptomatic over-anticoagulation in warfarin patients; dietary reference intake for healthy adults is on the order of 90–120 mcg/day, distinct from these therapeutic doses

Route

Oral in the cited reversal trial; also available as an injectable (phytonadione) for clinical use

Frequency studied

Single oral dose in the reversal-of-anticoagulation study cited here

Half-life

Reported on the order of a few hours in circulation, consistent with its role as a rapidly acting coagulation factor precursor

Timing

with a meal

With food

with food

OTC supplementVitamin K1 (phytonadione) is available both as an FDA-approved prescription injectable/oral product for anticoagulation reversal and as an over-the-counter dietary supplement at nutritional dosesTherapeutic reversal doses used in the cited trial are far higher than routine dietary-supplement doses and were administered under clinical supervisionLongevity

Key references

  1. Phylloquinone (Vitamin K1): Occurrence, Biosynthesis and Functions (2017)
  2. Reversal of asymptomatic over-anticoagulation by orally administered vitamin K (2006)

Studied ranges, not dosing advice. Not medical advice — talk to a clinician. doseroutine.com/library/vitamin-k1

Cite this page

Using this in an article, AI answer, or research note? Please attribute:

DoseRoutine. (2026). Vitamin K1 — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/vitamin-k1
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