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. The 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 .
In contrast, 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 symptoms we discuss here are commonly associated with vitamin K deficiency, but are insufficient for a diagnosis. Work with your doctor to discover what underlying condition might be causing your low levels of this vitamin and to develop an appropriate plan to improve your health.
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
If you or your baby have several of these symptoms, seek immediate medical attention so that your doctor can effectively diagnose and treat vitamin K deficiency.
Vitamin K Deficiency Causes
Causes shown here are commonly associated with vitamin K deficiency. Work with your doctor or other health care professional for an accurate diagnosis.
Vitamin K deficiency can occur if you are not taking in or absorbing enough of this vitamin. Since it abounds in many foods, vitamin K deficiency is rare in healthy adults eating a varied diet.
You have a higher risk of deficiency if you are:
- Pregnant [3, 10, 11, 12]
- Suffering from a condition that impairs nutrient absorption in the gut, such as celiac disease, Crohn’s disease, or cystic fibrosis [13, 14, 15]
- Taking blood thinners 
- Older [16, 17, 18]
- Hospitalized due to critical illness [19, 20, 21, 22, 23]
- Have chronic kidney disease [24, 25]
- Have cancer [26, 27, 28]
1) Dietary Deficiency
The recommended adequate intake (AI) of vitamin K is 90 mcg/day for women and 120 mcg/day for men .
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 .
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, 29, 30].
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 [31, 32, 33].
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 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 [34, 35, 36, 37, 38, 39].
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 [40, 41, 42, 43].
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 [44, 45, 46].
Cystic fibrosis damages the liver and pancreas. Six studies on over 600 people with this condition revealed that 70-95% had vitamin K deficiency, especially those who also had liver cirrhosis [15, 47, 48, 49, 50, 51].
Vitamin K is routinely given to people with cystic fibrosis to prevent deficiency and bleeding disorders [52, 53, 54, 55, 56, 57, 58].
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 [59+, 60, 61, 62].
If the disorder occurs during pregnancy, high blood bile and low vitamin K levels increase the risk of potentially deadly bleeding in the fetus [63, 64].
Bleeding due to vitamin K deficiency is an early sign of blocked bile ducts in newborns. It’s commonly resolved with vitamin K [65, 66, 67, 68, 69].
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 [13+, 70]:
- 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 [71, 72, 73, 74, 75, 76, 77].
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 .
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 [14+, 79, 80+, 81, 82, 78, 83, 84].
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 [85+, 86, 87, 88, 89+, 90+, 91, 92+].
Vitamin K supplements can help. They reduced the risk of bone loss in a study on almost 200 people with short bowel syndrome .
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 [94+].
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 [95, 96, 97, 98].
Vitamin K deficiency from weight-loss surgery is more dangerous in pregnant women. It may cause life-threatening bleeding in their babies [99, 100, 101].
Other conditions causing vitamin K deficiency from reduced fat uptake include:
3) Certain Medications
The following medications may cause or worsen vitamin K deficiency, especially when taken for long periods or at high doses. Consult your doctor if you are taking them and experience vitamin K deficiency symptoms. Do not change their dose and frequency or stop taking them without your doctor’s approval.
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 [105, 106, 107].
Antibiotics may cause vitamin K deficiency by killing the gut bacteria that produce it. Cephalosporin antibiotics may additionally block vitamin K action in the body. However, vitamin K supplementation is only needed in case of long-term antibiotic use .
Additionally, taking broad-spectrum antibiotics for too long may cause deficiency by killing the gut bacteria that produce vitamin K2 [109, 110, 111+].
Drugs that block fat and cholesterol uptake may also cause vitamin K deficiency. They include:
- Bile acid sequestrants (e.g., cholestyramine) 
- Lipase blockers (e.g., orlistat) 
- Cholesterol uptake blockers (e.g., ezetimibe) 
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 [115, 116, 117].
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 [118, 119, 120].
Make sure to inform your doctor if you have vitamin K deficiency and are taking vitamin E supplements or eating a high-vitamin E diet.
5) Populations at High Risk
Because the following groups of people are at an increased risk of vitamin K deficiency, their levels of this vitamin should be carefully monitored.
Babies are at higher risk of vitamin K deficiency because :
- 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 the 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, 122, 123, 124].
The growing fetus takes vitamin K from the mother’s bloodstream and may cause a slight, normally harmless deficiency [125, 10+].
In contrast, 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 [63, 126, 91, 100]
- Uncontrolled use of blood thinners or anti-seizure medication [127, 128]
- Eating disorders 
- A severe pregnancy sickness with vomiting and weight loss (hyperemesis gravidarum) [11, 12]
Several studies found a poorer vitamin K status in elderly people. The main reasons for this deficiency were [16, 17+, 18+]:
- Reduced dietary intake
- Higher use of antibiotics and blood thinners
- Likely to have conditions that reduce its absorption
Vitamin K deficiency with bleeding disorders was common in 6 studies on over 200 adults and 69 children in the ICU. The main causes for this deficiency were [19, 20, 21, 22, 23, 129]:
- Inadequate diet
- Poor health status that reduced vitamin K uptake
- Antibiotic therapy
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 [26, 130, 27+, 28+].
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 .
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 [132, 133, 134, 135, 136, 137, 24, 25, 138, 139, 140, 141].
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 .
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 [143, 144].
Vitamin K Deficiency Diagnosis & Tests
Your doctor will take your medical history to assess whether you are at risk of vitamin K deficiency. Next, he or she may order a blood test to see how long it takes your blood to clot. This helps your doctor determine if vitamin K deficiency underlies your symptoms.
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) [145+, 146+, 147].
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 [148+].
High levels of inactivated vitamin K-dependent proteins (such as prothrombin, osteocalcin, and MGP) in the blood also indicate vitamin K deficiency .
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 .
In urine tests, vitamin K deficiency causes lower levels of its byproducts (gamma-carboxyglutamic acid, aglycones, and menadione) [150, 151, 152].
Lab results are commonly shown as a set of values known as a “reference range”, which is sometimes referred to as a “normal range”. A reference range includes the upper and lower limits of a lab test based on a group of otherwise healthy people.
Your healthcare provider will compare your lab test results with reference values to see if your chloride results fall outside the range of expected values. By doing so, you and your healthcare provider can gain clues to help identify possible conditions or diseases.
Remember that some lab-to-lab variability occurs due to differences in equipment, techniques, and chemicals used. Don’t panic if your result is slightly out of range – as long as it’s in the normal range based on the laboratory that did the testing, your value is normal.
However, it’s important to remember that a normal test doesn’t mean a particular medical condition is absent. Your doctor will interpret your results in conjunction with your medical history and other test results.
And remember that a single test isn’t enough to make a diagnosis. Your doctor will interpret this test, taking into account your medical history and other tests. A result that is slightly low/high may not be of medical significance, as this test often varies from day to day and from person to person.
Vitamin K Deficiency Treatment & Prevention
The most important thing is to work with your doctor to treat any underlying conditions causing your low vitamin K levels. You may make dietary changes or take vitamin K supplements if you and your doctor determine that they could help you prevent vitamin K deficiency.
The usual treatment for vitamin K deficiency is oral or injected vitamin K1. The normal dose ranges from 1 to 25 mg/day [54, 82].
In people on blood thinners, the dose is reduced to 1-10 mg/day to prevent drug interactions .
In cases with very severe bleeding, fresh frozen blood can be given instead [154+].
You can prevent vitamin K deficiency by eating sufficient amounts of foods rich in [155, 156+, 157+]:
- 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 .
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.
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.