Coughing up a large amount of blood
(more than 100mL in a 24hr period) is a medical emergency.
Regardless, any coughing
up of blood (hemoptysis) is a serious symptom. There are many causes of this. This includes airways disease (such as bronchitis, cancer, airway trauma), pulmonary disease (tuberculosis, pneumonia), immune disorders, pulmonary thromboembolism, heart conditions (valve disease), or blood disorders.