Waking up with blood in the mouth may be caused by trauma to the oral mucosa, localized inflammation of the periodontium of the teeth, or long-term use of drugs or diseases with blood clotting disorders. 1. Trauma. When there are bad restorations or sharp tooth roots in the mouth, the buccal or lingual mucosa may be accidentally damaged during sleep and cause bleeding. 2. Periodontal inflammation of the teeth. When there is pulpitis, apical periodontitis or long-term chronic periodontal inflammation, blood seepage in the mouth can also occur. 3. Long-term medication. When suffering from cardiovascular disease if long-term use of aspirin, warfarin and other anticoagulant drugs, gums are also prone to bleeding. 4. Blood clotting disorders. Leukemia, hemophilia and other coagulation disorders, gums have a tendency to spontaneous bleeding. Waking up with blood in the mouth can be seen in a variety of causes, specific recommendations to the hospital to confirm the examination.