Coughing up blood can be alarming, but it is often caused by common, treatable conditions like a respiratory infection or a severe coughing fit. There is no specific over-the-counter medicine you should take without a doctor's diagnosis, as treating the underlying cause is essential. For instance, if an infection is responsible, a doctor may prescribe antibiotics. If a harsh cough is causing it, a generic cough suppressant like dextromethorphan might be recommended after evaluation. Please seek medical attention promptly to get an accurate diagnosis. If you experience shortness of breath, chest pain, or cough up large amounts of blood, please go to the emergency room immediately.