Warfarin (brand names Coumadin or Jantoven) is by far the cheapest blood thinner available to patients to prevent deadly blood clots. However, new research suggests that warfarin might not be the best choice when considering patient bone health.

A recent retrospective study from researchers associated with the University of Minnesota School of Public Health found that warfarin had a modestly higher risk of bone fractures compared to other kinds of blood thinners (dabigatran, brand name Pradaxa, rivaroxaban, brand name Xarelto and apixaban, brand name Eliquis). This finding was more pronounced in patients being treated for atrial fibrillation who also had osteoporosis.

An x-ray of a bone fracture, which may have been caused by Warfarin.
An x-ray of a bone fracture. Photo by Harlie Raethel on Unsplash.

Their findings shared a similar conclusion to a 2017 study from Hong Kong that found that warfarin had a higher risk of bone fractures in patients being treated for atrial fibrillation who had a history of falls and/or fractures, compared to dabigatran. 

Warfarin works by blocking an enzyme called vitamin K epoxide reductase, which is important for recycling a form of vitamin K needed to synthesize components of the blood coagulation cascade. The coagulation cascade, which makes blood clots to prevent the body from bleeding out after injury, can be targeted by blood thinners to prevent inappropriate blood clots from forming and clogging blood vessels. The problem with warfarin was that it also affected the vitamin K needed to make bone matrix proteins to strengthen bones. 

The researchers suggested caution when considering prescribing warfarin to atrial fibrillation patients with a high risk of fracture, and this risk should be weighed against financial burdens patients might face to maintain treatment.


Lutsey PL, Norby FL, Ensrud KE, et al. Association of Anticoagulant Therapy With Risk of Fracture Among Patients With Atrial Fibrillation.JAMA Intern Med.Published online November 25, 2019. doi:10.1001/jamainternmed.2019.5679

Lau WCY, Chan EW, Cheung C, et al. Association Between Dabigatran vs Warfarin and Risk of Osteoporotic Fractures Among Patients With Nonvalvular Atrial Fibrillation.JAMA.2017;317(11):1151–1158. doi:10.1001/jama.2017.1363