Bladderwrack Seaweed & Warfarin

Publication Date: 
Fri, 02/01/2013
By: Alere Staff

Bladderwrack, also known as Black Tang, is a type of seaweed. It is the most common type of seaweed found in the ocean. It is often dark green with air pods that allows the seaweed to remain on the sea surface. People use the whole seaweed plant to make medicine, although there is not enough scientific evidence to show whether or not it is effective for any medical condition.

Some people use bladderwrack for thyroid disorders, arthritis, heartburn, and even applied to the skin for burns, or insect bites. It is not safe to eat bladderwrack, but it is available in supplement pill form.

Interactions with warfarin?

The Natural Medicines Comprehensive Database lists bladderwrack as a ‘theoretical’ interaction with anticoagulants such as warfarin, meaning it may interact with warfarin. Bladderwrack may slow blood clotting1, so talk to your doctor before consuming any bladderwrack products.

Increasing testing frequency is recommended when starting or stopping any new medication or dietary supplement including vitamins. Home INR monitoring will help improve your control of warfarin. More frequent testing, typically performed by patient self testing, is a valuable tool for detecting rises and falls in INR values and enable you to work with your clinician to make any adjustments to diet or medication dosing.2 Go to the Getting Started page for more information about testing your INR at home.

  1. Durig J, Bruhn T, Zurborn KH, et al. Anticoagulant fucoidan fractions from Fucus vesiculosus induce platelet activation in vitro. Thromb Res 1997;85:479-91.
  2. Center for Medicare and Medicaid Services. Decision Memo for Prothrombin Time (INR) Monitor for Home Anticoagulation Management (CAG-00087R) [Memorandum]. 2008. Baltimore, MD.