Warfarin doubles stroke risk in first week, study finds AF treatment with warfarin initially doubles the risk of stroke before lowering it, research suggests. by Stephen Robinson Sign in to continue Sign In Email address Password Stay signed in Trouble signing in? Reset password: Click here Need help? Email us Register FREE Limited free articles a month Free email bulletins Register Now Register Now Take a 30-day trial Join MIMS now and pay nothing for the first 30 days Join GPOnline now and pay nothing for the first 30 days Sign Up Sign Up