Is Vitamin K Safe?

• G6PD Deficiency
• Drug & Supplement Interactions
• Lab Tests

Taking vitamin K supplements and ingesting vitamin K in your food is generally considered safe for adults and children. Both vitamin K1 and vitamin K2 have been used safely in clinical trials, including long-term clinical studies (up to 3 years) and intravenously. Not enough studies have been done in pregnant women to determine its safety for fetuses, so pregnant women should seek the advice of their doctor before taking vitamin K supplements.^(1, 4, 12)

Allergic reactions have been reported with injectable vitamin K and are generally mild. However, on very rare occasions, intravenous vitamin K has been linked to potentially fatal allergic reactions. Vitamin K3 is no longer used to treat vitamin K deficiency because it has caused liver toxicity, jaundice, and anemia in infants.^(1, 4, 12)

Vitamin K, VKDB, and Childhood Cancers

Vitamin K deficiency bleeding (VKDB) is a life-threatening condition that causes hemorrhaging in newborn babies. It's easily treated with an injection of 0.5-1 mg of vitamin K.^(4, 12)

Two studies in the 1990s reviewing case data suggested that vitamin K injections given to newborn infants were possibly linked to childhood cancers (e.g., leukemia). However, they have since been refuted by much larger and case-controlled research involving over a million medical records.⁽⁴⁾

The American Academy of Pediatrics continues to recommend vitamin K treatment for newborns at risk of the life-threatening condition VKDB.^(4, 12)

Safety Concerns with G6PD Deficiency

G6PD deficiency is a common genetic condition found in millions of people. G6PD enzymes are necessary to protect cells from free radicals. Red blood cells are even more susceptible to free radical damage, and without protection they break down rapidly.⁽¹³⁾

Certain foods, infections, drugs, and natural supplements can trigger episodes of rapid blood cell breakdown (called hemolysis) and anemia. Vitamin K was suspected to be a trigger, and some medical experts caution people with G6PD deficiency to avoid vitamin K.^{(13, 14)}

However, a recent systematic analysis of all clinical studies linking vitamin K to hemolysis found no evidence of harm for vitamin K. Other suspected triggers, such as vitamin C, vitamin E, Gingko biloba, and alpha lipoic acid were also cleared (based on current clinical evidence).⁽¹⁵⁾

Vitamin K Drug/Supplement Interactions

Vitamin K can have dangerous interactions with certain drugs. Conversely, some medications also affect vitamin K levels in the body. Severe vitamin K deficiency increases risk of serious bleeding because vitamin K is needed for clotting.⁽¹⁾

Vitamin K: Interactions with Lab Tests

Vitamin K may interfere with results of lab tests with a number of substances, either by altering levels of the substance or causing inaccurate results because of interference with the testing mechanism:^(1, 17)