There are a wide variety of medical issues that can cause a person to cough up blood including tuberculosis, cystic fibrosis, emphysema, lung cancer and drug use, explains Mayo Clinic. Additionally, a parasitic infection, mitral valve stenosis or pneumonia also can lead to coughing up blood.
Blood that comes from the respiratory tract or lungs is referred to as hemoptysis, according to Mayo Clinic. Blood coming from other areas such as the stomach can appear to be coming from a person's lungs. A person who is coughing up blood should call his doctor to determine the cause of bleeding. A person who is coughing up a large amount of blood or experiencing bleeding that cannot be stopped should call 911 immediately.
In some cases, the reason for coughing up blood is not identified and the condition improves within a six-month time frame, states WebMD. Testing that can help to identify the cause of hemoptysis are chest x-ray, computed tomography or CT scan, a bronchoscopy, a complete blood count or CBC, a physical exam and personal history. These tests center on determining the rate of bleeding that is occurring and whether there is a risk to breathing ability.