What Is Vitamin K Deficiency? | Nutrition

Vitamin K Deficiency

Overview of vitamin K deficiency

Vitamin K plays an important role in coagulation, better known as blood clotting. Clotting is a process that helps prevent excessive bleeding both inside and outside the body.

Your body needs vitamin K to produce the proteins that go to work during the clotting process. If you’re vitamin K deficient, your body doesn’t have enough of these proteins. The telltale sign of vitamin K deficiency is bleeding too much.

Scientists also believe that vitamin K helps bones grow and stay healthy, but they continue to study that relationship.

Vitamin K deficiency is rare in adults because many of the foods we eat contain adequate amounts of K1, and because the body makes K2 on its own. Plus, the body is good at recycling its existing supply of vitamin K. However, certain conditions and some drugs can interfere with vitamin K absorption and creation, making it possible to become deficient.

Vitamin K deficiency is much more common in infants. In infants, the condition is called VKDB, for vitamin K deficiency bleeding.

Symptoms of vitamin K deficiency

There are several symptoms associated with vitamin K deficiency. The main symptom is excessive bleeding.

Excessive bleeding may not be immediately evident, as it might only occur if the person gets a cut.

Additional signs of excessive bleeding can include:

  • Bruising easily
  • Small blood clots appearing under the nails
  • Bleeds in mucous membranes that line areas inside the body
  • Stool that is dark black, tar-like, or contains blood

When looking for signs of vitamin K deficiency in newborn babies and infants, doctors will also look for:

  • Bleeding from the area where the umbilical cord has been removed
  • Bleeding in the skin, nose, gastrointestinal tract, or other areas
  • Bleeding at the penis if the baby has been circumcised
  • Sudden brain bleeds, which are deemed severe and potentially life-threatening

Causes of vitamin K deficiency

Although vitamin K deficiency is uncommon in adults, certain people are at increased risk if they:

  • Take coumarin anticoagulants such as warfarin, which thins the blood
  • Taking antibiotics
  • A condition that causes the body to not absorb fat properly (fat malabsorption)
  • Have a diet that is extremely lacking in vitamin K

Coumarin anticoagulants interfere with the production of the proteins involved in blood clotting.

Some antibiotics cause the body to produce less of its own vitamin K. Other antibiotics may cause vitamin K to become less effective in the body.

Fat malabsorption leading to vitamin K deficiency may occur in people with:

  • Celiac disease
  • Cystic fibrosis
  • Disorder in the intestines or biliary tract (liver, gallbladder, and bile ducts)
  • Part of their intestine removed

Newborn infants are at increased risk for vitamin K deficiency for a variety of reasons:

  • Breast milk is very low in vitamin K.
  • Vitamin K does not transfer well from a mother’s placenta to her baby.
  • The liver of a newborn infant doesn’t use vitamin efficiently.
  • Newborns don’t produce vitamin K2 on their own in the first few days of life.

Risk factors

Side effects of oral vitamin K in recommended doses are very rare. Many medications interfere with the effects of vitamin K, including antacids, blood thinner antibiotic aspirin, and medications for cancer, and other conditions.


First, your doctor will need to know your medical history to understand if you’re at risk of becoming vitamin K deficient. People at risk are generally those who:

  • Take anticoagulants
  • Take antibiotics
  • Have a condition where fat absorption is a problem.

Most likely your doctor will perform a coagulation test called the prothrombin time (PT) test to see if a vitamin K deficiency is causing your symptoms. This is a blood test that measures how long it takes for your blood to clot.

A nurse, lab technician, or another healthcare professional trained at drawing blood will take a sample using a small needle. They will then add chemicals to the sample to see how it reacts. Blood usually takes about 11 to 13.5 seconds to clot. If the blood takes longer to clot, your doctor may determine that you are vitamin K deficient.

The lab may also look at the results in a different way, measuring the international normalized ratio (INR). INR is based on a scale that compares the results of different laboratories worldwide. A normal INR is about 0.9 to 1.1. For someone taking a blood thinner, it might be about 2 to 3.5. Your doctor will be looking to see if the number is too high.

Treatment for vitamin K deficiency

The treatment for vitamin K is the drug phytonadione, which is vitamin K1. Most of the time doctors prescribe it as an oral medication. A doctor or nurse might also inject it under the skin (as opposed to into a vein or muscle). The dosage for adults ranges from 1 to 25 milligrams (mg).

Doctors will prescribe a smaller phytonadione dose for someone who is taking an anticoagulant. Typically this dosage is about 1 to 10 mg. This is to avoid a complication due to anticoagulants interfering with the body’s vitamin K production.

In infants, the American Academy of Pediatrics recommends that newborns get a single shot of 0.5 to 1 mg vitamin K1 at birth. A higher dose may be necessary if the mother has been taking anticoagulants or anti-seizure drugs.

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