Receiving your lab test results can sometimes raise questions. A line concerning coagulation, such as TP/INR, might catch your attention. This value, sometimes outside the reference ranges, is often linked to the action of vitamin K. Understanding this parameter is essential to correctly interpret this information. This article guides you to decode what vitamin K is, its importance for your health, and the steps to take if your results indicate a variation.

What is Vitamin K? Its Key Role in Coagulation

Vitamin K is a family of fat-soluble vitamins. It plays a fundamental role in several bodily processes. Its most known action is its participation in blood coagulation.

The Different Forms of the Vitamin

There are mainly two important forms for humans:

• Vitamin K1 (phylloquinone): This is the most common form in our diet. It is found in abundance in green leafy vegetables like spinach, cabbage, and broccoli.
• Vitamin K2 (menaquinones): It is partially produced by bacteria in our intestinal flora. Some fermented foods (like natto) or animal products (liver, certain cheeses) also contain it.

Mechanism of Action in Coagulation

Your body obtains this vitamin through food. After its absorption in the intestine, it is transported to the liver. This is where it activates proteins essential for coagulation, called “coagulation factors”.

Imagine a cascade of dominoes. Vitamin K sets up these dominoes. When an injury occurs, the first domino falls and triggers a chain reaction. The final result is the formation of a clot that stops the bleeding. Without a sufficient amount of functional vitamin K, some of these dominoes are not ready, and the cascade is interrupted. For example, prothrombin, a major factor, needs this vitamin to function.

The Impact of This Vitamin on Your Overall Health

An imbalance in vitamin K action can have concrete consequences. Insufficient vitamin action increases the risk of bleeding. For example, you might notice easy bruising, nosebleeds, or heavier menstrual periods.

Beyond Coagulation: Bones and Arteries

Research has shown that vitamin K also plays a crucial role in other areas:

• Bone Health: Vitamin K, especially K2, activates osteocalcin. This protein helps to fix calcium onto bone structure, contributing to their strength. Insufficient vitamin K status could therefore weaken the skeleton in the long term.
• Cardiovascular Health: It activates another protein (MGP) which helps prevent calcium deposition on artery walls. This process, calcification, is a cardiovascular risk factor. Vitamin K thus helps maintain the flexibility of blood vessels.

Who is Affected by a Deviation?

Severe deficiency is rare in healthy adults. However, some populations are at higher risk. This includes newborns, people with chronic intestinal diseases (Crohn’s disease, celiac disease), or liver diseases. Taking certain medications, such as long-term antibiotics and especially anticoagulants (vitamin K antagonists), also represents a situation to monitor.

How to Read Your Lab Test Related to Vitamin K?

Most often, we don’t directly measure vitamin K levels. Instead, its effect on coagulation is measured through tests like Prothrombin Time (PT) and INR (International Normalized Ratio).

Deciphering a Result Line

Your report may present the following information in the “Hemostasis” section:

• Prothrombin Time (PT) ……. 85 % (Reference Ranges: 70 – 130 %)
• INR ………………………. 1.1 (Reference Ranges: 0.8 – 1.2)

PT measures clotting time as a percentage of a normal value. INR is a standardized ratio used to compare results between laboratories. A low PT or a high INR (outside of anticoagulant treatment) means the blood takes longer to clot.

Why Measure the Effect Rather Than the Vitamin Itself?

Direct measurement of vitamin K is complex and costly. More importantly, PT and INR reflect its actual biological activity. It is therefore a more relevant indicator of clinical risk. It allows checking if the coagulation mechanism is working at the correct speed.

Pathologies Related to Vitamin K Imbalance

A TP/INR result outside the norms is a signal. It indicates a disturbance in coagulation function.

Insufficient Action Level (Low PT / High INR)

This is the most common case. It indicates an increased risk of bleeding.

• Possible Causes: Very low dietary intake, intestinal malabsorption, liver disease, or medication use. Vitamin K antagonist (VKA) anticoagulants intentionally target this effect to thin the blood.
• Associated Symptoms: Easy bruising, bleeding gums or nosebleeds, heavy menstrual periods, prolonged bleeding after a cut.
• Further Tests: The doctor may order a liver panel or other tests to find the cause.

Excessive Action Level (High PT / Low INR)

This situation is much rarer in people not taking anticoagulants.

• Possible Causes: Excessive and uncontrolled vitamin K supplementation. In a patient undergoing VKA treatment, a sudden and massive intake of vitamin K (through diet or supplements) can counteract the treatment effect and increase the risk of clotting (thrombosis).
• Associated Symptoms: There are generally no direct symptoms, except in the case of complications in a patient treated with VKAs.

Practical Advice to Act on Your Vitamin K Status

Facing a deviation, concrete actions can be considered, always in consultation with your healthcare professional.

When to Consult?

• Slight deviation without symptoms: Discuss it during your next consultation.
• Significant deviation or symptoms: Consult your doctor promptly.
• Under VKA treatment: Follow your doctor’s recommendations for any adjustment.
• Significant bleeding: An emergency consultation is necessary.

Specific Nutritional Advice

If a deficiency is suspected (excluding VKA treatment), dietary adjustments can be beneficial.

• Increase K1 sources: Regularly include dark green vegetables: spinach, cabbage, broccoli, parsley.
• Think about K2: Natto, certain aged cheeses, and egg yolk are sources.
• Improve absorption: Combine these foods with a source of good fats like olive oil.

Intake Stability: The Golden Rule for Patients Under VKA

If you are being treated with vitamin K antagonist anticoagulants, stability is key. The goal is not to avoid foods rich in vitamin K, but to maintain a constant daily intake. Any major dietary change must be reported to your doctor, as your treatment dose will likely need to be adjusted.

Frequently Asked Questions About Vitamin K

Why Measure INR if I’m Not Taking Anticoagulants?

INR is a very reliable functional test that assesses the overall effectiveness of vitamin K-dependent coagulation. It can reveal a problem (like an unknown liver disease) even if vitamin K levels are normal. Furthermore, it is a quick, inexpensive, and well-standardized test.

Can a Course of Antibiotics Change My INR?

Yes, it is possible. Broad-spectrum antibiotics taken for a long time can reduce the intestinal bacteria that produce vitamin K2. This effect is generally modest and reversible upon stopping the treatment.

Abnormal INR with a Perfect Liver Panel, What to Do?

If the liver is functioning well and you are not taking VKAs, the doctor will explore other avenues. This may include subtle intestinal malabsorption, drug interactions, or, more rarely, a congenital deficiency.

Does Vitamin K Thicken the Blood?

This expression is a simplification. Vitamin K does not make the blood “thick”. It is essential for the coagulation process to occur normally. High intake through diet is not considered dangerous for a healthy person. The only risk concerns patients on VKAs, as an excess of vitamin K can counteract the effect of their treatment.

Does Vitamin K Deficiency Have Other Long-Term Effects?

Yes. Beyond the risk of bleeding, chronic deficiency, even slight, is associated with a higher risk of osteoporosis and may play a role in arterial calcification. Maintaining a correct status is therefore important for overall health.

Additional resources

• To deepen your knowledge of this blood marker, click here.
• To extend your knowledge and decipher other markers, more articles are available here.

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