Vitamin K Deficiency

Vitamin K deficiency reduces the body’s ability to activate clotting proteins (factors II, VII, IX, X, and proteins C and S). The result can be easy bruising, nosebleeds, gum bleeding, heavy periods, or prolonged bleeding after minor cuts or dental work. Adults may become deficient with poor intakefat-malabsorption (celiac, IBD, pancreatic or biliary disease, bariatric surgery), long courses of antibiotics, heavy alcohol use, or certain medicines that block vitamin K recycling.

A lab-first approach typically starts with PT/INR (prothrombin time) and may include PIVKA-II (des-γ-carboxy prothrombin, an uncarboxylated prothrombin), plasma vitamin K1, and a liver panel to separate deficiency from liver synthesis problems or anticoagulant drug effects. Testing supports screeningdiagnostic triage, and monitoring, but it does not replace a clinician’s exam, medication review, or emergency care for active bleeding.

Signs, Symptoms & Related Situations

  • Bleeding & bruising: easy bruising, frequent nosebleeds, gum bleeding, heavy or prolonged periods, bleeding after minor cuts or procedures

  • Skin & mucosa: petechiae (pinpoint spots), oozing from wounds

  • GI & stool clues: dark/tarry stools or blood in stool (urgent evaluation needed)

  • Risk contexts: low-fat or highly processed diets; fat-malabsorption (celiac, IBD, chronic pancreatitis, cystic fibrosis, cholestasis); bariatric surgeryprolonged broad-spectrum antibiotics; heavy alcohol intake

  • Medication flags: warfarin (vitamin K antagonist), some cephalosporins, bile-acid sequestrants; multiple drug–nutrient interactions

  • When to seek urgent care now: significant or uncontrolled bleeding, vomiting blood, black/bloody stools, sudden severe headache, weakness on one side, chest pain, or shortness of breath

Symptoms are nonspecific and should be evaluated by a qualified clinician.

Why These Tests Matter

What testing can do

  • Detect a vitamin K–related clotting problem with PT/INR and PIVKA-II

  • Differentiate deficiency from liver disease or medication effects using liver enzymes/bilirubin and a medication review

  • Monitor trends after clinician-directed nutrition or medication changes

What testing cannot do

  • Diagnose the exact cause of bleeding without a full medical evaluation

  • Replace imaging or procedures when internal bleeding is suspected

  • Provide dosing or treatment advice—review results with your clinician, especially if you take warfarin or other anticoagulants

What These Tests Measure (at a glance)

  • PT/INR (Prothrombin Time / International Normalized Ratio): first-line indicator; prolonged PT/INRsuggests reduced activity of vitamin K–dependent factors (VII often changes earliest). Also prolonged by warfarin and liver disease.

  • PIVKA-II (Des-γ-carboxy prothrombin): abnormal prothrombin made when vitamin K is insufficient; elevates in deficiency and some liver disorders.

  • Vitamin K1 (Phylloquinone), plasma: reflects recent intake; may be low in deficiency or malabsorption. Use with functional tests (PT/INR, PIVKA-II) for context.

  • Liver panel (ALT, AST, ALP, GGT, bilirubin) ± albumin: helps distinguish hepatic synthesis problems from pure vitamin K deficiency.

  • aPTT, fibrinogen, CBC (selected): broader hemostasis context; anemia may reflect occult blood loss.

  • Pre-analytical notes: follow collection instructions; some vitamin K1 assays prefer fasting, avoiding supplements and high-fat meals before the draw. Tell the lab if you take anticoagulants.

Quick Build Guide

Goal / Scenario Start with Add if needed
Bleeding/bruising, deficiency suspected PT/INR • Liver Panel PIVKA-II • Vitamin K1 (plasma) • CBC
On warfarin with high INR PT/INR Medication review with clinician; PIVKA-II or liver panel if unclear
Fat-malabsorption / bariatric / cholestasis PT/INR • Vitamin K1 • Liver Panel PIVKA-II • Fat-soluble vitamins (A, D, E)
Antibiotics >2–3 weeks PT/INR PIVKA-II • Vitamin K1 if abnormal or symptoms present
Alcohol-related liver risk PT/INR • Liver Panel • CBC PIVKA-II to help parse deficiency vs hepatic dysfunction
Follow-up after clinician changes PT/INR PIVKA-II to trend functional correction

How the Testing Process Works

  1. Match tests to your situation: start with PT/INR; add PIVKA-IIvitamin K1, and a liver panel based on history and medicines.

  2. Prepare for accuracy: share all medications and supplements (especially warfarin, antibiotics, bile-acid binders). Follow any fasting or supplement-hold directions for vitamin K1 testing.

  3. Provide samples: standard blood draw.

  4. Get secure results: most post within a few days.

  5. Plan next steps: review results with your clinician to confirm the cause (diet, absorption, liver disease, or drug effect) and to set a monitoring plan.

Interpreting Results (General Guidance)

  • Prolonged PT/INR + elevated PIVKA-II with low/normal liver enzymes → likely vitamin K deficiency or reduced intake/absorption.

  • Prolonged PT/INR + abnormal liver panel → consider hepatic dysfunction; deficiency can still coexist.

  • Low plasma vitamin K1 → suggests low intake or malabsorption; interpret with PT/INR and clinical context.

  • High INR while on warfarin → usually reflects the intended drug effect; do not change medications or take vitamin K without clinician guidance.
    Trends over time and the clinical picture matter more than one value; always interpret with a qualified healthcare professional.

Choosing Panels vs. Individual Tests

  • Core deficiency panel: PT/INR • PIVKA-II • Vitamin K1 (plasma) • Liver Panel

  • Broader bleeding workup (as directed): aPTT • Fibrinogen • CBC

  • Malabsorption context (selected): add fat-soluble vitamins (A, D, E)
    Use bundled panels for efficient screening; add targeted markers to answer specific questions and monitor progress.

FAQs

Do I need to fast for vitamin K testing?
Some vitamin K1 assays request fasting and avoiding supplements/high-fat meals beforehand. PT/INR does not require fasting.

Can antibiotics cause vitamin K deficiency?
Long courses can reduce gut bacteria that contribute to vitamin K supply, especially with low dietary intake or malabsorption.

My INR is high—does that mean I’m deficient?
Not necessarily. Warfarin and liver disease also raise INR. Your clinician will interpret results with your medication list and liver tests.

Is PIVKA-II only for liver cancer?
No. PIVKA-II rises in vitamin K deficiency and some liver diseases. It must be interpreted with other labs.

Should I take vitamin K before testing?
Do not self-treat. Supplements can change results and may be unsafe with anticoagulants. Ask your clinician first.

What foods contain vitamin K?
Leafy greens (vitamin K1) and some fermented foods (vitamin K2) are common sources—discuss diet changes with your clinician, especially if on warfarin.

Related Test Categories & Key Tests

  • All Vitamin & Mineral Tests

  • Mineral Deficiency Tests • Vitamin & Mineral Deficiency Tests • Liver Health Tests • Blood Coagulation Tests • Malabsorption Tests • Nutrition Tests

  • Key Tests: PT/INR • PIVKA-II (Des-γ-carboxy prothrombin) • Vitamin K1 (Phylloquinone), plasma • Liver Panel (ALT, AST, ALP, GGT, Bilirubin) • aPTT • Fibrinogen • CBC • Fat-Soluble Vitamins (A, D, E)

References

  • NIH Office of Dietary Supplements — Vitamin K Fact Sheet for Health Professionals.
  • American Society of Hematology — Evaluation of bleeding and coagulation disorders.
  • AACC (American Association for Clinical Chemistry) — Guidance on coagulation testing and interferences.
  • American College of Gastroenterology — Malabsorption and fat-soluble vitamin assessment.
  • Clinical reviews on PIVKA-II, vitamin K–dependent clotting factors, and interpretation of PT/INR in deficiency vs liver disease vs anticoagulants.

Available Tests & Panels

Your Vitamin K Deficiency Tests menu is pre-populated in the Ulta Lab Tests system. Start with PT/INR and add PIVKA-IIvitamin K1, and a liver panel to clarify cause and severity. Use filters to include aPTT, fibrinogen, and CBC when a broader bleeding workup is needed. Follow any prep instructions (especially for vitamin K1), and review results with your clinician to confirm findings and set a monitoring plan.

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The Vitamin K Test measures blood levels of vitamin K, a nutrient essential for blood clotting, bone strength, and heart health. Deficiency may cause easy bruising, excessive bleeding, or weakened bones, and can result from poor diet, liver disease, or malabsorption. Doctors order this test to investigate clotting problems, monitor anticoagulant therapy, or assess nutritional status. Results help guide treatment, supplementation, and long-term health management.

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The Protein C Activity Test measures the activity of protein C, a natural anticoagulant that regulates blood clotting. Low activity can indicate inherited or acquired protein C deficiency, increasing the risk of abnormal clot formation, deep vein thrombosis, or pulmonary embolism. This test supports evaluation of clotting disorders and provides insight into overall coagulation balance and vascular health.

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The Protein C Activity Test with Reflex to Protein C Antigen measures the functional activity of Protein C, a vitamin K–dependent anticoagulant that regulates clot formation. Low Protein C activity can increase the risk of abnormal blood clots and may result from congenital deficiency, liver disease, or vitamin K deficiency. Reflex testing to Protein C antigen helps distinguish between quantitative and functional deficiencies.


The Protein C Antigen Test measures the quantity of Protein C, a vitamin K–dependent anticoagulant that regulates clot formation. Low antigen levels may indicate inherited or acquired Protein C deficiency, which increases the risk of deep vein thrombosis or other clotting disorders. This test helps differentiate between quantitative and functional deficiencies when evaluating abnormal coagulation.

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The Prothrombin Time with INR Test measures how long it takes blood to clot and calculates the international normalized ratio (INR) for accuracy. It is commonly used to monitor patients on blood-thinning medications like warfarin and to evaluate bleeding disorders, liver disease, or vitamin K deficiency. Doctors order this test to investigate easy bruising, frequent nosebleeds, or prolonged bleeding and to ensure safe and effective anticoagulant therapy.

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Diagnosing Vitamin K Deficiency; the body requires small regular amounts of Vitamin K. This nutrient is important in the formation of coagulation factors, protein S, and protein C. When blood vessels are injured, all these substances help in the blood’s clotting. They also ensure excessive clotting is prevented. Easy bruising and extreme bleeding can be caused by inadequate vitamin K. Also, this nutrient has an important role when it comes to bone loss prevention. Low bone density has been associated with low levels of vitamin K within the blood. There is some evidence suggesting that enough vitamin K levels lead to bone health improvement. Such levels also reduce fracture risks.

Vitamin K exists in three different types:

  • Vitamin K1 comes from foods. It also goes by the name phylloquinone or phytomenadione. Green leafy vegetables, vegetable oils, and dairy products are the source of vitamin K1. It is regarded as vitamin K’s “plant form.” The commercial production of K1 is also done for the treatment of conditions linked to excess bleeding.  
  • Bacteria are used in the production of vitamin K2 (menaquinones). It is produced by the intestines’ normal flora. The conversion of K1 into K2 is made possible by intestinal bacteria. The body’s requirements are met when the diet is supplemented by vitamin K2.    
  • K3 (menadione) is a synthetic chemical compound that is non-natural. This nutritional supplement is used in some countries due to its vitamin K activity. Menadione supplements aren’t allowed for human use in the US due to their potential toxicity. The body must take in a certain amount of vitamin K through the diet since enough amounts of this nutrient aren’t produced by the body. This vitamin is present within many food varieties. It is normally supplied in enough levels in the regular diet in the USA.

Various foods contain high levels of vitamin K per serving. They usually exceed the Recommended Daily Allowance (RDA). These foods consist of leafy green vegetables, including spinach, kale, green leaf lettuce, and collards. Other vegetables such as asparagus, broccoli, cabbage, and brussels sprouts also fall under this category. Dairy products, soybeans, cereals, and vegetable oils also add up as other sources. Both K1 and K2 are fat-soluble. They are stored in the fat tissue and liver of the body. Vitamin K that’s worth a week is typically stored by an adult.

Factors That Result in Vitamin K Deficiency          

Insufficient dietary intake, decreased vitamin K storage because of liver disease, and inadequate absorption are the common causes that result in vitamin K deficiency. A decrease in its production within the intestines may also lead to its deficiency.

Healthy individuals in the US rarely experience dietary deficiency of vitamin K. This is, however, relatively common with individuals that have certain chronic conditions or are severely ill. For instance, it is commonly witnessed in patients suffering from serious illnesses such as cancer patients who are undergoing chemotherapy and chronic dialysis patients. It can also be seen in individuals at risk for malnutrition, such as those that have poor dietary habits that are linked to drug abuse or alcoholism.

Malabsorption can result in vitamin K deficiency. This can more so be caused by impaired fat absorption due to conditions such as celiac disease, Crohn’s disease or chronic pancreatitis, and cystic fibrosis. Malabsorption can also be caused by cholestatic liver diseases such as primary biliary cirrhosis or bile duct obstruction. This results in vitamin K deficiency. The absorption of vitamin K can be affected by medications such as antacids, antibiotics, as well as anti-seizure drugs. These medications can also affect the amount of K2 produced within the intestines or even lead to vitamin K’s degradation. Vitamin K requirements may be increased through the consumption of high aspirin doses.

Insufficient normal flora within the intestines of newborns can result in vitamin K deficiency. Vitamin K may also not be present in enough levels from breast milk. Also, vitamin K deficiency may occur once the infant is born if the infant’s mother was on certain medications such as anti-seizure medications while pregnant. These incidents are usually linked to vitamin K deficiency bleeding or VKDB. It is also referred to as hemorrhagic disease of the newborn. It can result in extreme bleeding and bruising. Severe cases may result in fatal brain bleeding.

VKDB was a relatively common occurrence in the past. Luckily, it has subsided since the introduction of the vitamin K injection that’s administered shortly after newborns are delivered. The American Academy of Pediatrics recommends its administration. Vitamin K may also be administered to help with excessive infant bleeding in instances where surgeries are required.   

A frequent question asked is if individuals that have used the anticoagulant drug warfarin in their treatment shouldn’t eat foods rich in vitamin K. It is also common for people to query whether the risk of vitamin K deficiency is heightened by limiting such foods after being treated with Coumadin®.

Individuals with various conditions, including cardiovascular diseases (CVD) and deep vein thrombosis (DVT), are prescribed with warfarin. It helps “thin” their blood. Inappropriate clotting is prevented using this drug. A test termed as PT/INR is usually done to determine how effective the dose “thins” the blood after the prescription of warfarin by a healthcare practitioner. The adjustment of this dose is determined by the test results. This adjustment ensures excessive bleeding is prevented through the prescription of the right amount of the dose.

The ability of the liver to use vitamin K in the production of blood-clotting factors is reduced by taking warfarin. This implies that an antagonism exists between warfarin and vitamin K. They counteract each other. The success of warfarin in the prevention of blood clots without resulting in excess bleeding is dependent on the significant decreases or increases in the vitamin K amounts consumed by an individual. Individuals who are under warfarin prescriptions need to take in a consistent amount of foods rich in vitamin K every day rather than avoid them. Through consistency in the food amount that’s consumed, these individuals can get their much-needed vitamin K.    

Signs and Symptoms

Vitamin K deficiency can be associated with the following signs and symptoms:

  • An increase in prothrombin time (PT/INR)
  • Intense menstrual periods
  • Urine and/or stool that contains blood
  • Easy bruising
  • Oozing from either gums or nose
  • Extreme bleeding from punctures, wounds, and surgical or injection sites
  • Bleeding from the GI (gastrointestinal) tract

The signs and symptoms mentioned above may be similar in vitamin K deficiency bleeding involving newborns. More serious cases in newborns involve intracranial hemorrhage. 

Questions may be raised on whether one is vitamin K deficient if the symptoms mentioned above are observed in an individual with an increased risk, say:

  • Individuals with chronic conditions linked to malabsorption or malnutrition
  • Individuals who’ve been undergoing treatment for a long-time using antibiotics; the medications act by killing the bacteria responsible for vitamin K2 production in the small intestine.
  • Severely sick patients such as dialysis or cancer patients

Tests      

Excessive or unexpected bleeding usually leads to the discovery of vitamin K deficiency. The principal laboratory test that’s conducted to examine the bleeding in such cases is the prothrombin time (PT/INR). The administration of vitamin K by injection is done if it is suspected that the bleeding may have been as a result of low vitamin K levels. An assumption is made that a vitamin K deficiency caused the bleeding if it stops, and the PT is normalized.

Occasionally, other coagulation tests may be performed to an individual with excessive bleeding and bruising symptoms. They include thrombin time, partial thromboplastin time (PTT), platelet function tests, platelet countfibrinogend-dimer, coagulation factor tests, and von Willebrand factor.