Vitamin K and Liver: The Complete Guide to Optimal Health

Jeux paralympiques

Vitamin K plays a key role in blood clotting — a process closely connected to the liver, which is the main organ responsible for storing and activating this vitamin. In cases of liver disease, vitamin K becomes particularly useful for reducing the risk of bleeding, even though it does not directly treat liver damage. A deficiency can worsen clotting disorders, while an excess of natural vitamin K is safe for the liver. Only the synthetic form (K3) poses a potential toxicity risk. Foods rich in vitamin K, such as green leafy vegetables and fermented products, are beneficial for liver health. Supplementation may be necessary for patients with cirrhosis or those taking certain medications. However, any intake of vitamin K should be medically supervised in cases of anticoagulant treatment or severe liver conditions.

TABLE OF CONTENTS

WHAT IS VITAMIN K?

Vitamin K is a fat-soluble vitamin, meaning it dissolves in fats and can be stored in the body, mainly in the liver. Vitamin K is essential for the proper functioning of the body. It plays a key role in processes such as blood clotting, bone strength, and various metabolic mechanisms.

There are mainly two natural forms of this vitamin:

  • Vitamin K1 (phylloquinone), which is found primarily in green leafy vegetables such as spinach, kale, broccoli, and lettuce.
  • Vitamin K2, also known as menaquinone, is partly produced by intestinal bacteria. It is also found in fermented foods such as natto (fermented soybeans), miso, certain aged cheeses, and liver.

A third synthetic form, called vitamin K3 (menadione), is sometimes used in veterinary medicine but is not recommended for human consumption because it can be toxic in high doses.

The main function of vitamin K is to ensure proper and efficient blood clotting. It is essential for the production of specific proteins that regulate this process. Without it, the body cannot stop bleeding effectively.

However, its importance goes beyond that. Vitamin K2 also plays a major role in binding calcium to bones (through activation of osteocalcin) and preventing calcium deposits in the arteries, making it a key nutrient for cardiovascular health.

Finally, the liver plays a central role in the metabolism of vitamin K: it stores, transforms, and uses it to activate clotting proteins. A poorly functioning liver can therefore interfere with vitamin K utilization, which underlines the importance of understanding how this vitamin works.

WHAT ROLE DOES VITAMIN K PLAY IN THE LIVER?

The liver plays a central role in the metabolism of vitamin K. It is responsible for both storing and converting it into its active form, allowing the production of key proteins involved in blood clotting. Without a properly functioning liver, vitamin K cannot fully perform its role, even if dietary intake is sufficient.

The production of clotting factors depends on vitamin K. One of vitamin K’s major roles in the liver is the production of clotting factors — proteins that enable blood to coagulate. These factors — particularly factors II (prothrombin), VII, IX, and X — can only be activated through vitamin K, which allows them to bind to calcium, an essential step for their function during bleeding or injury.

When there is a vitamin K deficiency or liver dysfunction, this synthesis process is disrupted, significantly increasing the risk of bleeding, even without trauma.

A close connection between liver disorders and vitamin K deficiency. People suffering from liver diseases (such as cirrhosis, chronic hepatitis, or liver failure) often develop a vitamin K deficiency. This is due to several factors: poor absorption of dietary fats (and therefore fat-soluble vitamins), reduced hepatic storage capacity, and impaired protein synthesis.

In these patients, symptoms such as frequent bleeding, unexplained bruising, or coagulation issues are often markers of a vitamin K deficiency.

Vitamin K as a therapeutic aid in liver disease. In certain medical situations, vitamin K is administered preventively or therapeutically to correct coagulation disorders caused by liver dysfunction. For example, after severe hepatitis or before surgery in a cirrhotic patient, vitamin K supplementation may be prescribed to help reduce hemorrhagic risk.

However, its effectiveness always depends on the liver’s ability to utilize it, which is why in advanced stages of liver disease, simple supplementation may not be sufficient.

A vital balance between vitamin K and liver health. The relationship between vitamin K and the liver is twofold: on one hand, the liver activates and stores vitamin K; on the other, vitamin K enables the liver to perform essential functions such as blood coagulation. A disruption in either one can lead to significant health issues. This is why monitoring vitamin K levels is crucial for people with liver conditions or coagulation disorders.

CAN A VITAMIN K DEFICIENCY AFFECT THE LIVER?

Understanding vitamin K deficiency. In healthy adults, vitamin K deficiency is relatively rare because this vitamin is widely available through diet and partially synthesized by gut bacteria. However, certain medical conditions — such as liver disease, fat absorption disorders, or prolonged antibiotic use — can lead to a deficiency. This lack directly affects blood clotting, but its consequences go beyond that.

The liver as an indirect victim of vitamin K deficiency. The liver is not structurally damaged by a vitamin K deficiency, but it suffers functionally. When vitamin K levels are too low, the liver can no longer properly produce coagulation proteins, weakening the entire hemostatic system. This can cause internal bleeding, including within liver tissues themselves, which can worsen hepatic stress.

Moreover, the liver is also involved in activating vitamin K. When it is weakened or diseased, it may further worsen the deficiency by reducing the efficient conversion of vitamin K into its active forms.

Increased risks in pre-existing liver diseases. For individuals suffering from liver conditions such as cirrhosis, chronic hepatitis, or cholestatic diseases, a vitamin K deficiency can have even more severe effects. These patients are already prone to coagulation disorders, and the deficiency further increases the risk of complications — such as hematomas, digestive bleeding, or postoperative hemorrhages.

In this context, vitamin K acts as a supportive tool — not to "treat" the liver directly, but to reduce bleeding risks caused by its dysfunction.

Vitamin K: an indirect marker of liver health. A vitamin K deficiency can sometimes serve as an early indicator of undiagnosed liver dysfunction. If the liver can no longer activate vitamin K or synthesize the proteins that depend on it, this may signal an existing impairment. This is why physicians often monitor coagulation markers (such as prothrombin time) in at-risk patients, as they indirectly reflect liver health.

A two-way relationship. The connection between vitamin K and the liver is reciprocal. On one hand, a weakened liver can cause vitamin K deficiency, and on the other, a vitamin K deficiency can worsen liver function. Although vitamin K does not directly treat liver diseases, it plays a vital supportive role in limiting complications and maintaining essential bodily functions.

WHICH VITAMIN K-RICH FOODS ARE GOOD FOR THE LIVER?

Food as the main source of vitamin K.

Vitamin K is mainly found in two types of foods depending on its form: vitamin K1 (phylloquinone), mostly present in green leafy vegetables, and vitamin K2 (menaquinone), found in fermented foods and some animal sources. Eating a varied diet rich in these foods not only helps meet daily vitamin K needs but also contributes indirectly to good liver function.

Green leafy vegetables: a natural source of vitamin K1.

Green leafy vegetables are by far the richest source of vitamin K1. In addition to their fiber, antioxidants, and chlorophyll content, they also contain compounds that support liver detoxification.

Some of the best choices for liver health include:

  • Kale
  • Spinach
  • Broccoli
  • Arugula
  • Fresh parsley
  • Romaine lettuce
  • Brussels sprouts

These vegetables also promote digestion and weight regulation — two key factors in preventing liver diseases such as fatty liver (steatosis).

Fermented foods: a valuable source of vitamin K2.

Vitamin K2 is less common in Western diets but plays a crucial complementary role to vitamin K1, particularly for cardiovascular and bone health. It also helps regulate calcium metabolism, which can indirectly ease the liver’s workload by preventing unwanted mineral deposits.

Good sources include:

  • Natto (fermented soybeans, extremely rich in K2)
  • Some aged cheeses (such as gouda and emmental)
  • Miso
  • Unpasteurized sauerkraut
  • Kefir (naturally fermented)

These foods also support gut microbiota, improving overall nutrient absorption — including fat-soluble vitamins such as vitamin K.

Organ meats and fatty fish: beneficial when consumed in moderation.

Certain animal products provide vitamin K2, along with iron, B vitamins, and omega-3 fatty acids — all beneficial for liver health.

Top sources include:

  • Chicken liver (rich in K2 and iron)
  • Calf liver
  • Mackerel
  • Sardines
  • Wild salmon

However, they should be consumed in moderation, especially for those with liver overload or high cholesterol.

Foods to include in a holistic liver support diet.

In addition to direct vitamin K sources, it is wise to include other foods that naturally support the liver:

  • Artichoke – stimulates bile production
  • Black radish – aids detoxification
  • Turmeric – has anti-inflammatory properties
  • Garlic – supports liver enzyme activity
  • Citrus fruits – rich in antioxidants

These foods may not all contain vitamin K, but when combined with green vegetables and fermented foods, they create a favorable environment for optimal liver health.

Varying sources to nourish the liver and maintain balance.

To maintain healthy vitamin K levels while supporting the liver, it is recommended to regularly consume green vegetables — preferably raw or lightly cooked — include fermented foods in your diet, and moderate your intake of animal products rich in vitamin K2. A balanced diet remains the key to a healthy liver capable of efficiently absorbing and using this essential vitamin.

SHOULD VITAMIN K BE AVOIDED IN CASE OF LIVER DISEASE?

A common misconception: Is vitamin K dangerous for a damaged liver?

Some people with liver disease may fear that taking vitamin K could overload the liver or worsen their condition. In reality, vitamin K is not toxic to the liver, even when it is weakened. On the contrary, in many cases, it can play a supportive role by reducing complications linked to coagulation disorders.

Vitamin K becomes even more crucial when the liver is diseased.

The liver is responsible for producing clotting factors, a process that directly depends on vitamin K. In cases of liver disease (such as cirrhosis, hepatitis, or liver failure), this synthesis is often impaired, increasing the risk of bleeding. Vitamin K then becomes an essential cofactor to activate the remaining functional coagulation proteins.

Therefore, rather than avoiding it, it is sometimes necessary to administer vitamin K under medical supervision to reduce the risk of internal bleeding or complications during medical procedures.

When should vitamin K intake be monitored?

Although vitamin K is beneficial in most liver conditions, certain situations require special attention:

  • For patients taking anticoagulants (such as warfarin or other VKAs): vitamin K can interfere with the effects of these drugs. It is crucial to monitor dosages and coagulation levels (INR) regularly.
  • In cases of cholestasis or fat malabsorption (often present in hepato-biliary diseases), the absorption of fat-soluble vitamin K may be reduced. Supplementation — sometimes by injection — may be required.
  • For patients with severe liver failure, the liver’s ability to properly use vitamin K may be compromised. In these cases, the effect of supplementation will depend on the severity of liver damage.

Medical use of vitamin K in liver-related conditions.

In hospital or medical settings, vitamin K is often used to:

  • Treat coagulation disorders in people with cirrhosis.
  • Prepare liver patients for surgical procedures.
  • Treat bleeding caused by vitamin K deficiency.
  • Reverse the effects of an overdose of oral anticoagulants.

Vitamin K may be administered orally, intramuscularly, or intravenously, depending on the clinical situation.

It’s not about avoiding vitamin K, but about adjusting its use to the patient’s needs.

In cases of liver disease, vitamin K should not be avoided but rather adapted according to the patient’s condition. Far from being harmful, it can actually prevent serious complications — provided it is administered carefully, especially when combined with anticoagulant therapy. As always, medical advice is essential to determine the correct dosage and form of supplementation.

WHAT ARE THE SIDE EFFECTS OF EXCESS VITAMIN K ON THE LIVER?

Is vitamin K toxic in excess?

Whether it comes from food (as K1 or K2) or from supplements, vitamin K is generally well absorbed and tolerated by the body. Unlike other fat-soluble vitamins (such as vitamin A or D), toxicity from excess natural vitamin K in adults is extremely rare. No upper limit (UL) has been established for natural forms, as no serious adverse effects have been documented from high dietary intakes.

Is the liver affected by excess natural vitamin K?

In healthy individuals, the liver efficiently regulates vitamin K levels through natural mechanisms that prevent unnecessary accumulation. It uses what it needs to activate clotting proteins and stores only a small amount in its tissues. The excess is either metabolized or excreted.

No serious studies have shown that excessive intake of vitamin K1 (from green vegetables) or K2 (from fermented or animal-based foods) causes liver toxicity. Therefore, the liver is not at risk from high levels of natural vitamin K obtained from food or moderate supplementation.

Vitamin K3 (synthetic): a real risk for the liver.

The actual liver risk comes from vitamin K3, or menadione — a synthetic form once used in some supplements and veterinary applications. This form is no longer allowed in human dietary supplements in most countries due to its potential toxicity.

Exposure to high doses of vitamin K3 has been linked to liver damage, including hepatic cell necrosis, oxidative stress, and impaired liver function. These effects have mainly been observed in infants, laboratory animals, or cases of deliberate overdose. Today, vitamin K3 use is strictly regulated and is not found in standard dietary supplements.

General side effects of excess vitamin K (beyond the liver).

Although liver-related effects are nearly nonexistent for natural forms, excessive or inappropriate vitamin K intake may occasionally cause:

  • Coagulation disturbances in people taking anticoagulants (interaction)
  • Rare allergic reactions
  • Temporary increases in liver enzyme levels (in very rare cases)
  • In infants, jaundice or hyperbilirubinemia, mainly with the K3 form

Again, these cases are rare and usually occur in poorly supervised medical contexts.

Caution with synthetic forms, not with natural ones.

In summary, natural forms of vitamin K pose no known risk to the liver, even at high doses, when obtained from food or high-quality supplements. In contrast, synthetic vitamin K3 — now largely discontinued — can cause liver toxicity. It is therefore essential to choose safe, well-formulated sources and avoid excessive self-supplementation, especially in people with liver conditions or those taking anticoagulant medications.

CAN PEOPLE WITH CIRRHOSIS TAKE VITAMIN K?

Cirrhosis and coagulation disorders: a close connection.

Cirrhosis is a chronic liver disease characterized by progressive destruction of liver tissue, which is gradually replaced by fibrosis. This process severely affects the liver’s ability to perform its essential functions — one of the most important being the synthesis of clotting factors, which are highly dependent on vitamin K. As a result, people with cirrhosis often suffer from coagulation disorders, leading to an increased risk of bleeding.

Vitamin K: a helpful support, but not a cure for cirrhosis.

For individuals with cirrhosis, vitamin K can help correct certain coagulation abnormalities, especially when a deficiency is identified. It is sometimes given preventively before a medical procedure or in cases of unexplained bleeding.

However, it is important to understand that vitamin K does not treat cirrhosis itself. When the liver’s ability to produce proteins is severely impaired, vitamin K supplementation alone may not be enough to normalize clotting. Its effectiveness depends largely on the extent of liver damage.

When is vitamin K supplementation recommended?

Supplementation is generally considered in the following situations:

  • Confirmed vitamin K deficiency due to poor fat absorption or insufficient dietary intake
  • Before surgery or invasive procedures to reduce the risk of bleeding
  • Active bleeding or unexplained coagulation disorders
  • Prolonged prothrombin time that can be normalized with vitamin K

In all cases, supplementation must be medically supervised, as coagulation markers can also be affected by factors unrelated to vitamin K.

Is there a risk in taking vitamin K with cirrhosis?

In most cases, vitamin K is well tolerated, even in people with cirrhosis. It does not burden or damage the liver further. The main risks come not from vitamin K itself, but from potential interactions with anticoagulant medications or from misinterpreting the cause of a coagulation problem.

For example, if a cirrhotic patient has a prolonged coagulation time that does not improve with vitamin K, it may indicate that the liver is too damaged to respond — not that the vitamin is ineffective or harmful.

Conclusion: yes, but under medical supervision.

People with cirrhosis can — and sometimes should — take vitamin K, especially when a deficiency is suspected or confirmed. When used properly, it can reduce bleeding risks and improve certain biological parameters. However, supplementation must always be prescribed and monitored by a doctor, taking into account liver function, current treatments, and overall therapeutic goals. It’s not a vitamin to avoid, but one to use wisely.

DO LIVER MEDICATIONS INTERFERE WITH VITAMIN K?

The liver: a key hub for the metabolism of many drugs and vitamin K.

The liver plays a central role in processing active substances, whether they are medications or fat-soluble vitamins like vitamin K. When we talk about possible “interference,” it means that certain medications used to treat liver conditions can affect the absorption, activation, or effectiveness of vitamin K — or conversely, that vitamin K can influence how certain drugs work.

Some treatments can reduce vitamin K activity or absorption.

Several types of medications commonly prescribed for liver conditions can lower vitamin K levels or activity:

  • Broad-spectrum antibiotics: by destroying part of the gut microbiota, they reduce the natural production of vitamin K2 by intestinal bacteria.
  • Bile acid sequestrants (such as cholestyramine): used to treat certain biliary disorders or cholestasis, they reduce fat absorption — and therefore the absorption of fat-soluble vitamins like K.
  • Certain antituberculosis or anticonvulsant drugs can speed up the hepatic breakdown of vitamin K, reducing its concentration in the blood.
  • Oral anticoagulants (such as warfarin or VKAs): although not designed to treat liver issues, they act as direct antagonists of vitamin K, blocking the activation of vitamin K–dependent clotting factors. Their effect can be increased or weakened depending on vitamin K intake.

Hepatoprotective medications and vitamin K: no direct interference.

“Hepatoprotective” drugs — such as silymarin (from milk thistle) or ursodeoxycholic acid (used for cholestasis) — do not have any known negative interactions with vitamin K. On the contrary, some natural supplements that support liver health may actually improve the use of fat-soluble vitamins by enhancing fat digestion.

However, it’s always recommended to inform your doctor or pharmacist about all supplements you take, including vitamins, to avoid unexpected interactions with other medications.

Should vitamin K intake be adjusted depending on medication?

In some cases, yes. If a patient is on medication that affects the absorption or metabolism of vitamin K, medical monitoring is recommended. This may include:

  • Assessing coagulation markers, such as INR or prothrombin time.
  • Adjusting vitamin K doses (orally or by injection).
  • Balancing the diet to increase natural vitamin K intake.

Any supplementation should be done under medical supervision — especially if the patient is also taking anticoagulants.

Possible, but manageable interactions.

Certain medications used for liver disorders can interfere with vitamin K by reducing its absorption or altering its metabolism. This does not mean they are incompatible, but they must be monitored together. Most of these interactions are well-known and can be effectively managed with proper medical follow-up. Therefore, it’s important to never combine liver medications and vitamin K supplements without consulting a healthcare professional.

COACH'S TIPS

It’s not so easy to find isolated vitamin K — most of the time, it’s included in broader vitamin and mineral complexes. Normally, a balanced diet is enough to provide the amount of vitamin K the body needs.

Yves Bondroit coach for QNT

Posted in: Our tips

Back to blog

Related posts

Blog navigation

Blog categories

View all categories

Popular posts

View all popular posts