Spitting out blood, medically known as hemoptysis, can be caused by a number of conditions ranging from mild to serious. Common causes include gum disease (gingivitis), respiratory infections such as bronchitis or pneumonia, irritation from violent coughing, and nosebleeds. More serious causes include chronic lung diseases like bronchiectasis, pulmonary embolism (blood clot in the lungs), tuberculosis, lung cancer, or trauma to the mouth or throat area. Certain medications like blood thinners can also increase the risk of bleeding leading to blood in saliva or sputum. If the blood is coming from the mouth, it could also be due to mouth ulcers, injury, or gum disease. If the blood is coughed up with mucus, it may be related to the lungs or airways. Because spitting out blood can signal a potentially serious condition, it is important to seek medical evaluation promptly, especially if the bleeding is heavy, persistent, or accompanied by other symptoms such as chest pain, difficulty breathing, or fever.