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?
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 .
Signs & Symptoms of Vitamin K Deficiency
- Excessive bleeding from wounds or tissue lining
- Internal bleeding
- Bruising easily
- Heavy menstrual periods
- Blood clots under the nails
- Dark or bloody stools
- 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 .
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, 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].
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 [15, 16, 17, 18, 19, 20].
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].
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
- 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].
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 .
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].
Other conditions causing vitamin K deficiency from reduced fat uptake include:
3) Certain Medications
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].
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 [103, 104, 105].
5) Populations at High Risk
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 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].
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 
- A severe pregnancy sickness with vomiting and weight loss (hyperemesis gravidarum) [118, 119]
- Reduced dietary intake
- Higher use of antibiotics and blood thinners
- Likely to have conditions that reduce its absorption
- 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 [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 .
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 .
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].
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+].
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 .
Vitamin K Deficiency Treatment & Prevention
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 [158+].
- 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
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.
Get Vitamin K Supplements
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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.