People may feel light-headed and short of breath and have chest pain, and the skin may be cool, sweaty, or bluish.
Doctors do a chest x-ray to make the diagnosis.
People are given fluids intravenously or a blood transfusion, and a tube is inserted in the chest to drain the blood.

(See also Introduction to Chest Injuries.)
Hemothorax can result from any injury—blunt or penetrating―that cuts or tears a lung or an artery or vein in the chest. Blood may then accumulate in the pleural space―between the two layers of tissue that cover the lungs. A large amount of blood may press on the lungs and make breathing difficult. When air as well as blood enters this space, the disorder is called hemopneumothorax. Occasionally, hemothorax is caused by chest surgery or another disorder, such as tuberculosis or lung cancer.