Effect of Body Weight on Dose of Vitamin K Antagonists

Timothy H. Self, PharmD; Jessica L. Wallace, PharmD, BCPS; Sami Sakaan, PharmD, BCPS; Christopher W. Sands, MD


South Med J. 2015;108(10):637-643. 

In This Article

Abstract and Introduction


Objectives: Numerous factors are well documented to affect the response to vitamin K antagonists (VKA), including dietary vitamin K, other drugs, age, pharmacogenetics, and disease states. Body weight is perhaps not as well known as a variable affecting VKA dose. Our aim was to review the literature regarding body weight and VKA dose requirements.

Methods: We reviewed the English-language literature via PubMed and Scopus using the search terms VKA, warfarin, acenocoumarol, phenprocoumon, fluindione, AND body weight.

Results: Among 32 studies conducted since the widespread use of the international normalized ratio, 29 found a correlation with body weight or body surface area and VKA dose requirement. Warfarin was evaluated in 27 studies and acenocoumarol, phenprocoumon, or fluindione were assessed in 5 investigations.

Conclusions: Because of varying study methodologies, further study is warranted. Based on current evidence, clinicians should include body weight, along with other established variables when dosing VKA. Most important, obese and morbidly obese patients may require a 30% to 50% increase with the initial dosing of VKA.


Numerous factors are well documented to alter the response to vitamin K antagonists (VKA), including age, dietary vitamin K, disease states, drug interactions, and pharmacogenetics.[1] Two studies in the 1970s addressed body weight and warfarin dose.[2,3] Within the past few years, body weight has been assessed more frequently regarding its potential effect on the dose requirement for VKA.[4–31] Although most of these studies have examined the effect of body weight on warfarin, some investigations have included phenprocoumon, acenocoumarol, and fluindione.[11,32–35] The purpose of this review article is to summarize the evidence regarding body weight and VKA dose.