Vitamin K and Bleeding — “What is Vitamin K Good For?”

Joseph R. Anticaglia MD
Medical Advisory Board

We’ve all had a bloody nose, scraped a knee or cut a finger at one time or another. A remarkable feat happens when liquid blood turns into a solid mass forming a blood clot and the bleeding stops. If a wound, internal or external does not clot, the bleeding continues leading to shock and a catastrophic ending!

Surgeons are particularly attentive to the ability of patients to form blood clots. Prior to surgery, they routinely obtain a relevant bleeding history and laboratory tests which include a prothrombin time, also called PT or INR. It’s a blood test which indicates the time it takes for your blood to clot. They appreciate the important functions of vitamin K.

Vitamin K, a fat-soluble vitamin, is necessary to stop the bleeding and begin the healing process. It helps in the formation of prothrombin, a protein produced by your liver. Prothrombin is one of many factors in the blood needed by the body to form blood clots.

Functions of Vitamin K

The main job of vitamin K is to activate proteins that cause the blood to clot. Vitamin K works only if there is a deficiency of this vitamin. For instance, it does not stop the bleeding of patients with hemophilia due to other factors in their blood.

Some people take blood thinners, anticoagulants, for a variety of medical conditions. For example, persons with heart problems, those who have suffered a stroke or who have other medical problems take blood thinners. Warfarin is a common anticoagulant that interferes with vitamin K’s ability to form clots. Such individuals might experience a minor cut that “takes a long time to stop bleeding.”

Another job of vitamin K is assist in the formation of bone and its repair. Reduced bone mass and an increased incident of bone fractures have been associated with low blood levels of vitamin K.

There are Two Main Forms of Vitamin K:

Vitamin K1 is found in green leafy vegetable like spinach, kale and collard greens. When you eat vitamin K, your intestines direct it into the lymphatic system and from there into the blood. Vitamin K1 can interfere with actions of blood thinners making them less effective.

On the other hand, aspirin-like products and sulfa-related antibiotics are examples that can interfere with vitamin’s K’s ability to form clots. Vitamin K1 has been given orally or by injection to treat this problem.

Vitamin K2 is thought to slow down bone loss and decrease bone fractures by directing calcium toward bones and away from arteries. It helps to prevent osteoporosis (weak bones) and atherosclerosis hardening of the arteries.

There are two main Sources of Vitamin K

Reduction of Vitamin K Absorption

Bile is a fluid made by the liver and stored in the gallbladder. Bile salts are a component of bile which the body needs to absorb vitamin K. Intestinal diseases, liver diseases, oral antibiotics and overuse of mineral oil as a laxative can reduce the absorption of vitamin K.

Vitamin K Deficiency

Although rare, bleeding and hemorrhage can be signs of severe vitamin K deficiency. A prolonged prothrombin time is clinically relevant and places the individual at risk to bleed more easily. Vitamin K deficiency can:

VKDB — Vitamin K Deficiency Bleeding

All babies at birth have low levels of vitamin K because the vitamin has difficulty crossing the placenta during pregnancy. The American Academy of Pediatrics for the past fifty seven years has recommended vitamin K injections for all newborns.

In recent times, some parents have refused to give permission for doctors to administer vitamin K injections to their newly born child. This decision by parents places their infants at risk for Vitamin K deficiency bleeding. VKDB is a rare but potentially life threatening since it can lead to intracranial hemorrhage (bleeding within the brain).



  1. NIH; Vitamin K; September 26, 2018
  2. CDC; Vitamin K Deficiency Bleeding; Sept. 15, 2017
  3. Anticaglia, Joseph R; Vitamin Basics, Doctor’s Column, HC Smart, 2019 Haelle, Tare; More Parents Nixing Anti-Bleeding Shots for Their Newborns; Scientific America, August 19, 2014 Shearer MJ; Vitamin K deficiency bleeding (VKDB) in early infancy; Blood Review, March 23, 2009

This article is intended solely as a learning experience. Please consult your physician for diagnostic and treatment options.