If you are healthy and eating a varied diet, you probably don’t need to worry about vitamin K deficiency. But people with gut issues, those taking blood thinners, and babies are at risk. Read on to learn about the causes, symptoms, and prevention steps you can take.

What is Vitamin K Deficiency?

Vitamin K is an essential, fat-soluble vitamin. Initially discovered for its role in blood clotting, it also prevents artery hardening, brain damage, and bone loss [1+, 2].

Nature provides vitamin K in two forms: K1 in leafy greens and K2 in animal-based and fermented foods. Your gut bacteria can also make vitamin K2 from the K1 form [1+, 2].

Deficiency occurs if you are not taking in or absorbing enough vitamin K. Since it abounds in many foods, vitamin K deficiency is rare in healthy adults eating a varied diet [3].

In turn, it’s relatively common in babies, people on blood thinners, or those with problems absorbing fats [4, 5+].

Signs & Symptoms of Vitamin K Deficiency

The main symptom of vitamin K deficiency is poor blood clotting, resulting in [4, 6, 5+]:

  • Excessive bleeding from wounds or tissue lining
  • Internal bleeding
  • Bruising easily
  • Heavy menstrual periods
  • Blood clots under the nails
  • Dark or bloody stools

In babies, vitamin K deficiency may also involve bleeding [4, 7+, 8+, 9]:

  • Within the skull
  • From the umbilical cord stump and penis (if circumcised)
  • In the nose, skin, and digestive tract

Vitamin K Deficiency Causes

1) Dietary Deficiency

The recommended adequate intake (AI) of vitamin K is 90 mcg/day for women and 120 mcg/day for men [3].

But how was this adequate intake defined to begin with? Researchers have criticized it, since this is simply the amount at which people won’t uncontrollably bleed. The intake linked to good health has yet to be set [3].

Though rare, some people still struggle to get enough vitamin K – either due to poor diet or eating disorders.

In 2 clinical trials on 42 people, diets lacking green leafy vegetables (K1 food sources) reduced vitamin K blood levels. This, in turn, deactivated vitamin K-dependent proteins, which is typical of deficiency [3, 10, 11].

In an observational study, 54 women with anorexia had vitamin K deficiency and were at risk of bone loss. Eating disorders are especially dangerous in pregnant women, as they raise the risk of vitamin K deficiency in newborns [12, 13, 14].

Anorexia and diets low in vitamin K can cause deficiency, although this is uncommon.

2) Poor Fat Digestion

Liver and pancreas health are essential for digesting fats: the liver makes bile, while the pancreas produces digestive enzymes. Diseases affecting either of these organs reduce the body’s ability to break down, absorb, and use fat-soluble vitamins.

Liver Disease

Liver and bile duct disorders were associated with vitamin K deficiency in 2 studies on 90 adults and 15 children. Similarly, liver failure and liver cancer both increased a marker of vitamin K deficiency (PIVKA-II) in 4 studies on almost 650 people [15, 16, 17, 18, 19, 20].

However, supplementing probably won’t help. Vitamin K didn’t improve gut bleeding in people with liver diseases in studies and analyses on over 450 people [21, 22, 23, 24].

Pancreatic Inflammation

In 3 small studies on 54 people, pancreatic inflammation was accompanied by vitamin K deficiency. Some also experienced bleeding disorders and bone loss as a result [25, 26, 27].

Cystic Fibrosis

Cystic fibrosis damages the liver and pancreas. Six studies on over 600 people revealed that 70-95% had vitamin K deficiency, especially those with liver cirrhosis [28, 29, 30, 31, 32, 33].

Vitamin K is routinely given to people with cystic fibrosis to prevent deficiency and bleeding disorders [34, 35, 36, 37, 38, 39, 40].

Blocked Bile Flow

Liver, pancreatic, or gallbladder diseases can block bile flow, which reduces vitamin K absorption. Vitamin K deficiency and poor blood clotting were common in studies on over 100 people with blocked bile ducts [41+, 42, 43, 44].

If the disorder occurs during pregnancy, high blood bile and low vitamin K levels increase the risk of potentially deadly bleeding in the fetus [45, 46].

Bleeding due to vitamin K deficiency is an early sign of blocked bile ducts in newborns. It’s commonly resolved with vitamin K [47, 48, 49, 50, 51].

Liver, bile, and pancreas diseases can cause vitamin K deficiency by reducing its absorption from food.

3) Poor Fat Absorption (Gut Issues)

Because vitamin K is fat-soluble, conditions that reduce fat uptake in the gut may cause deficiencies.

Inflammatory Bowel Disease

People with IBD have lower blood vitamin K levels, due to several factors [52+, 53]:

  • Strict diets
  • Less efficient absorption of fat-soluble vitamins from gut inflammation
  • Altered gut bacteria that fail to produce vitamin K2

IBD was linked to poor vitamin K status and bone health in 4 studies on almost 200 adults and 63 children. Deficiency also increases the risk of bleeding in babies born to women with IBD [54, 55, 56, 57, 58, 59, 60].

Celiac Disease

In celiac disease, an exaggerated immune response to foods with gluten damages the gut lining. As a result, people with celiac disease can’t absorb fat-soluble vitamins as well as they should [61].

Several cases of vitamin K deficiency with bleeding disorders and bone loss have been reported in people with uncontrolled celiac disease. They all improved with vitamin K supplementation and a gluten-free diet [62+, 63, 64+, 65, 66, 61, 67, 68].

Short Bowel Syndrome

People with short bowel syndrome – due to surgical removal or severe damage – have reduced gut function and nutrient uptake. They also frequently suffer from vitamin K deficiency and bleeding disorders or bone loss. Women with the syndrome are at an increased risk of giving birth to children with vitamin K deficiency [69+, 70, 71, 72, 73+, 74+, 75, 76+].

Vitamin K supplements can help. They reduced the risk of bone loss in a study on almost 200 people with short bowel syndrome [77].

Weight-Loss Surgery

Some types of weight-loss surgery, such as gastric bypass, directly connect the stomach to the last part of the small bowel to reduce fat uptake in the gut. In addition to weight loss, they may cause nutrient deficiencies [78+].

In 3 studies on almost 300 people, weight-loss surgery caused unusually low levels of vitamin K and other fat-soluble vitamins. Nevertheless, a small study on 10 people found their deficiency was insufficient to cause bleeding disorders [79, 80, 81, 82].

Vitamin K deficiency from weight-loss surgery is more dangerous in pregnant women. It may cause life-threatening bleeding in their babies [83, 84, 85].

Other Conditions

Other conditions causing vitamin K deficiency from reduced fat uptake include:

  • Low levels of fat-transporting proteins (apolipoproteinemia) [86+, 87]
  • Bile acid deficiency [88]
All conditions that damage the gut and weaken its ability to absorb nutrients can cause vitamin K deficiency. IBD and celiac disease are two major ones.

3) Certain Medications

Blood Thinners

Blood thinners such as warfarin reduce blood clotting by blocking vitamin K regeneration. Taken for long or at excessive doses, they may cause vitamin K deficiency and bleeding disorders [89, 90, 91].

Antibiotics

As blood thinners, cephalosporin antibiotics also block vitamin K regeneration, increasing the risk of deficiency [92+, 93, 94, 95, 96].

Additionally, taking broad-spectrum antibiotics for too long may cause deficiency by killing the gut bacteria that produce vitamin K2 [97, 98, 99+].

Fat Blockers

Drugs that block fat and cholesterol uptake may also cause vitamin K deficiency. They include:

4) Too Much Vitamin E

Doctors have long known that Vitamin E overdose can cause bleeding disorders. In a study on 70 people, high doses increased marker of vitamin K deficiency(PIVKA-II). But moderate doses prevented blood clotting in another study on almost 40k women [103, 104, 105].

Animal studies found that both vitamins share the same production pathway. An excess of vitamin E blocks the conversion of vitamin K1 to K2 outside the liver [106, 107, 108].

5) Populations at High Risk

Babies

Babies are at higher risk of vitamin K deficiency because [109]:

  • Unborn babies receive little vitamin K through the placenta
  • Premature babies start their feeding later and often require antibiotics, which delays the growth of vitamin K-producing bacteria in their gut
  • Breast milk and some formulas are poor in vitamin K

Most countries routinely give newborns vitamin K to prevent bleeding. Although this practice was linked with risk of childhood leukemia in the 90s, further research didn’t confirm this association. Nevertheless, some parents believe that this measure is dangerous or unnecessary and refuse it, putting their babies at risk [4, 110, 111, 112].

Pregnant Women

The growing fetus takes vitamin K from the mother’s bloodstream and may cause a slight, normally harmless deficiency [113, 114+].

In turn, severe vitamin K deficiency during pregnancy is especially dangerous to the fetus. It may cause bleeding, birth anomalies, and even death. The most common causes include:

  • Conditions that reduce vitamin K uptake [45, 115, 75, 84]
  • Uncontrolled use of blood thinners or anti-seizure medication [116, 117]
  • Eating disorders [14]
  • A severe pregnancy sickness with vomiting and weight loss (hyperemesis gravidarum) [118, 119]

Elderly People

Several studies found a poorer vitamin K status in elderly people. The main reasons for this deficiency were [120, 121+, 122+]:

  • Reduced dietary intake
  • Higher use of antibiotics and blood thinners
  • Likely to have conditions that reduce its absorption

Critically-ill People

Vitamin K deficiency with bleeding disorders was common in 6 studies on over 200 adults and 69 children at the ICU. The main causes for this deficiency were [123, 124, 125, 126, 127, 128]:

  • Inadequate diet
  • Poor health status that reduced vitamin K uptake
  • Antibiotic therapy
Cancer

People with cancer often have nutrient deficiencies due to the well-known nausea and appetite loss caused by anticancer drugs. Specific cancers further suppress appetite and impair nutrient absorption.

Vitamin K deficiency was frequent in 2 studies on 46 adults and 26 children with cancer. Supplementation reduced the deficiency and prevented bleeding in 2 small studies on 21 people [129, 130, 131+, 132+].

Chronic Kidney Disease

People with chronic kidney disease are often prescribed a low-potassium or low-phosphate diet, which can lack vitamin K-rich foods such as leafy greens and dairy. To make matters worse, they require more vitamin K to maintain blood vessel health [133].

Eight studies on almost 700 people linked chronic kidney disease with poor vitamin K status. Vitamin K2 increased a marker that may prevent blood vessel calcification (blood activated MGP) in 4 trials on over 300 people [134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145].

Alcohol and Drug Addiction

People with alcohol and drug abuse are at an increased risk of nutrient deficiencies. They tend to eat less, while the addictive substance itself often lowers the absorption and use of nutrients [146].

In a study on 20 alcoholic men, 60% had vitamin K deficiency. Similarly, alcohol abuse during pregnancy was associated with a lower intake of vitamin K and other nutrients in a study on over 100 low-income women [147, 148].

Populations at a much higher risk of vitamin K deficiency include pregnant women, babies, the elderly and critically-ill, and people with addictions.

Diagnosis & Tests

A blood clotting test called prothrombin time is mainly used to diagnose deficiency in people with bleeding symptoms.

The blood sample is mixed with a clot-promoting reagent in the lab. An unusually long clotting time (over 11-13 seconds) confirms bleeding disorders. The result is standardized by comparing it to the average time of tests using the same reagent (international normalized ratio or INR) [149+, 150+, 151].

A vitamin K injection is often given after the test. If it reduces prothrombin time, it confirms that the bleeding disorder is indeed due to vitamin K deficiency [152+].

High levels of inactivated vitamin K-dependent proteins (such as prothrombin, osteocalcin, and MGP) in the blood also indicate vitamin K deficiency [153].

Blood levels of both vitamin K1 and K2 can also be measured directly. But they are rarely used since the procedure is difficult and their levels variable [153].

In urine tests, vitamin K deficiency causes lower levels of its byproducts (gamma-carboxyglutamic acid, aglycones, and menadione) [154, 155, 156].

A high prothrombin time is the most common blood marker of vitamin K deficiency. Other blood or urine markers may provide additional clues.

Vitamin K Deficiency Treatment & Prevention

Treatment

The usual treatment for vitamin K deficiency is oral or injected vitamin K1. The normal dose ranges from 1 to 25 mg/day [36, 66].

In people on blood thinners, the dose is reduced to 1-10 mg/day to prevent drug interactions [157].

In cases with very severe bleeding, fresh frozen blood can be given instead [158+].

Prevention

You can prevent vitamin K deficiency by eating sufficient amounts of foods rich in [159, 160+, 161+]:

  • Vitamin K1, such as kale, spinach, broccoli, cabbage, and vegetable oils
  • Vitamin K2, such as natto, foie gras and liver, dairies, egg yolks, and poultry meat

Combining these foods with fats, eating more fiber (to support your microbiome), and digestive enzyme supplements may improve vitamin K absorption.

In babies, vitamin K (normally as a single shot of 0.5-1 mg vitamin K1) helps prevent deficiency and bleeding [4].

People at high risk of vitamin K deficiency, such as those with poor fat absorption or taking blood thinners, should speak to their doctor about dietary changes, taking supplements, and monitoring their vitamin K levels.

Get Vitamin K Supplements

Irregular Results?

If you have irregular labs related to vitamin K deficiency or other nutrients, LabTestAnalyzer can help you make sense of them. It marks all your labs outside the optimal range and guides on how to get into that range naturally. You can also use it to track your labs over time. No need to do thousands of hours of research to understand your test results.

LabTestAnalyzer is a sister company of SelfHacked. This post contains sponsored links, which means that we may receive a small percentage of profit from your purchase, while the price remains the same to you. The proceeds from your purchase are reinvested into our research and development, in order to serve you better. Thank you for your support.

Takeaway

If you’re healthy and eating diverse foods, you shouldn’t worry about vitamin K deficiency. 

You may be at risk if you have health problems with your liver, pancreas, or gut. In this case, you may get enough dietary vitamin K but can’t absorb it well. Sensitive groups (pregnant women, newborns, the elderly and terminally-ill) and people on certain medications are also at a higher risk. 

Vitamin K injections treat severe deficiency, while supplements help with mild forms. The best way to make sure you get enough of this vitamin is to eat more foods rich in it. Take these foods together with healthy fats and look to additionally support your digestion with probiotics.

About the Author

Carlos Tello, PhD (Molecular Biology)

PhD (Molecular Biology)

Carlos received his PhD and MS from the Universidad de Sevilla.

Carlos spent 9 years in the laboratory investigating mineral transport in plants. He then started working as a freelancer, mainly in science writing, editing, and consulting. Carlos is passionate about learning the mechanisms behind biological processes and communicating science to both academic and non-academic audiences. He strongly believes that scientific literacy is crucial to maintain a healthy lifestyle and avoid falling for scams.

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