Spitting with dark red blood may be caused by oral bleeding, gastrointestinal bleeding, upper respiratory tract bleeding and other reasons. 1. Oral bleeding: bleeding from the surface of ulcers in the acute stage of oral ulcers, gingival inflammatory bleeding, blood system disorders such as leukemia and other conditions that lead to coagulation dysfunction bleeding and so on, so there will be this symptom. 2. Bleeding from digestive tract: bleeding from the surface of gastroduodenal ulcer, bleeding from gastric mucous membrane erosion in acute gastritis, bleeding from esophageal cancer and other malignant tumors after necrosis, rupture and bleeding of esophagogastric fundal varices, etc. Blood enters into the oral cavity from the stomach in the case of nausea, acid reflux, etc., and so this symptom will appear. 3. Bleeding from upper respiratory tract: viral infection leads to acute pharyngitis, pharyngeal edema and congestion; bronchial dilatation leads to pulmonary vascular malformation, small aneurysms rupture and bleeding during repeated coughing; tuberculosis, pneumonia and other infectious diseases of the lungs lead to increased permeability of pulmonary capillaries and bleeding, bleeding in the upper respiratory tract enters into the oral cavity when coughing, and thus this symptom occurs. Spitting dark red blood may be related to a variety of factors, it is recommended to seek medical attention to clarify the diagnosis.