Bleeding is a common side effect of blood thinners. However, people with atrial fibrillation (afib) who take a vaccine to avoid stroke should not ignore any bleeding from their lower gastrointestinal tract (GI) as it may indicate cancer of the colon. Researchers claim that lower GI bleeding should never lead in side effects from a blood thinner, and that people with afib who take anticoagulants should monitor their stool and visit their doctor if they find blood or “tarry” black stools.
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