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Why do you cough up blood?
Hemoptysis is defined as the coughing up of blood originating from the respiratory tract, typically expelled through a fit of coughing, either as pure blood or mixed together with mucus.
It is important to understand from the start that hemoptysis is not itself a disease, but rather a symptom through which a wide range of different underlying conditions can manifest. In most cases, the underlying cause is an inflammatory condition affecting the airways, such as bronchitis, pneumonia, or tuberculosis. However, one particularly important and serious cause of hemoptysis that should never be overlooked is lung cancer.
Coughing up blood can understandably be a frightening experience for both patients and their family members. However, it is worth emphasizing, particularly for younger and otherwise healthy individuals, that this symptom is generally not associated with serious underlying disease in this population.
This reassurance is an important point to keep in mind as you read through this article, which will focus primarily on the more serious and less common causes of hemoptysis, since these are the situations requiring the greatest medical attention and the most detailed explanation. In the vast majority of episodes affecting both adults and children, it is relatively common to cough up small amounts of bright red blood, or a frothy, blood-streaked sputum (a mixture of saliva and mucus originating from the lungs), most often as a direct result of prolonged coughing and/or a respiratory tract infection.
This symptom occurs in approximately 10% of patients with underlying lung disease and is observed, on average, in about 0.1% of all outpatient visits and 0.2% of all hospital admissions each year, making it a relatively uncommon but clinically significant presenting symptom.
The majority of hemoptysis cases occur in adults, with an average patient age of around 62 years, and most often in men, with a male-to-female ratio of approximately 2:1. In contrast, the presence of blood in a child’s coughed-up sputum is a relatively rare occurrence and generally warrants prompt medical evaluation given its rarity in this age group.
While hemoptysis can, in certain cases, represent a genuine, potentially life-threatening emergency requiring rapid diagnosis and treatment, it is important to know that over 90% of cases are self-limiting, meaning they resolve on their own without requiring aggressive intervention. That said, identifying the specific underlying cause can often prove quite challenging for physicians, and in a meaningful proportion of patients, the exact trigger unfortunately remains unidentified even after thorough evaluation.
It is also important to distinguish hemoptysis from situations involving darker blood mixed with food residue, which is more likely to indicate a gastrointestinal source of bleeding rather than a respiratory one. This distinct condition, known as hematemesis (vomiting blood), requires immediate evaluation in an emergency department, just as respiratory hemoptysis does, but points toward a very different underlying cause and diagnostic pathway.
What Should You Do?
If you experience coughing up blood, it is always advisable to consult your primary care physician. However, it is particularly important to seek medical attention urgently if any of the following apply:
- the amount of blood coughed up exceeds approximately one tablespoon,
- the episode of hemoptysis occurs frequently or repeatedly over a short period,
- the bleeding is accompanied by loss of appetite and/or unexplained weight loss, which together could suggest an underlying malignancy or chronic infectious process requiring prompt investigation.
When Should You Worry?
You should seek immediate care at an emergency department if hemoptysis is accompanied by any of the following serious or unusual symptoms:
- the loss of a substantial amount of blood,
- chest pain,
- dizziness,
- confusion,
- shortness of breath,
- an increased breathing rate,
- loss of consciousness,
- a bluish discoloration of the skin (cyanosis), which indicates dangerously low blood oxygen levels.
These warning signs suggest that the underlying bleeding may be significant enough to compromise breathing and oxygen delivery to the body, representing a genuine medical emergency that requires immediate professional evaluation and treatment.
Classification
The term “true hemoptysis” is used to describe the coughing up of blood from the mouth, typically triggered by a fit of coughing, in cases where the actual source of bleeding is located within the airways or lungs themselves.
When traces of blood originating from the airways are mixed together with mucus, the more technically accurate term is “hemoptoe” (blood-streaked sputum), a term that is frequently, though somewhat incorrectly, used interchangeably with true hemoptysis in everyday clinical language.
True hemoptysis must also be carefully distinguished from what is known as pseudohemoptysis, a condition in which the blood actually originates from a source outside the lower respiratory tract, including:
- the upper gastrointestinal tract (mouth, throat, or esophagus),
- the upper respiratory tract (mouth, nose, or throat).
Distinguishing between these two conditions requires a careful review of the patient’s clinical history along with a thorough physical examination of the throat and mouth. Beyond this clinical assessment, doctors can differentiate true hemoptysis from pseudohemoptysis by carefully evaluating specific characteristics of the expelled material and the patient’s associated symptoms:
True Hemoptysis
- Blood tends to have an alkaline (basic) pH, appears bright red, and often has a frothy or foamy texture due to mixture with air and mucus from the lungs.
- Patients most commonly present with associated breathing difficulty and a sensation of warmth or tickling within the chest.
Pseudohemoptysis
- Blood tends to have an acidic pH, appears darker in color, and often contains visible food particles or residue.
- Patients most commonly present with associated symptoms such as abdominal pain, nausea, and melena (digested blood appearing as dark, tarry stools).
Hemoptysis can also be classified based on the overall severity and volume of bleeding involved:
- sputum that is merely streaked or lightly tinged with blood,
- mild to moderate bleeding, involving a more noticeable but still limited volume of blood,
- massive hemoptysis, representing a severe, high-volume bleeding episode.
The consequences of hemoptysis can vary dramatically depending on the severity of the bleeding involved. Massive hemoptysis, in particular, can rapidly fill the airways with blood, leading to asphyxiation and death if not treated immediately, which is why this particular form requires far more urgent intervention than the milder forms described above. To be formally classified as “massive”, hemoptysis generally must involve the loss of approximately 500 milliliters of blood or more within a 24-hour period.
Causes
There are numerous possible causes underlying the presence of blood following a fit of coughing. In general terms, these causes can be organized into three broad categories:
- pulmonary (lung-related) diseases,
- cardiovascular diseases,
- other, less common causes.
It is worth noting that in approximately 50% of cases, despite thorough investigation, the specific underlying cause of hemoptysis ultimately remains unidentified, a phenomenon referred to as idiopathic or cryptogenic hemoptysis.
Pulmonary Causes
Among the lung-related conditions capable of causing hemoptysis are:
- respiratory tract infections,
- bronchitis,
- pneumonia,
- lung abscesses,
- lung cancer,
- lung metastases originating from cancers elsewhere in the body,
- bronchiectasis (a chronic condition involving abnormal widening of the airways),
- cystic fibrosis,
- pulmonary edema (fluid accumulation in the lungs),
- tuberculosis,
- aspergilloma (a fungal mass that can form within pre-existing lung cavities),
- benign lung tumors,
- vasculitis (inflammation of blood vessels),
- Behçet’s syndrome,
- granulomatosis with polyangiitis (GPA, formerly known as Wegener’s granulomatosis),
- Goodpasture syndrome, a rare autoimmune condition affecting both the lungs and kidneys.
Cardiovascular Causes
Among the conditions of cardiovascular origin capable of causing hemoptysis are:
- pulmonary embolism (a blood clot that travels to and blocks an artery in the lungs),
- vascular malformations,
- pulmonary arteriovenous malformation (pAVM), an abnormal connection between pulmonary arteries and veins,
- pulmonary artery aneurysms,
- aortobronchial fistula, an abnormal connection between the aorta and the bronchial airways,
- Rendu-Osler-Weber disease (hereditary hemorrhagic telangiectasia), a genetic condition causing abnormal blood vessel formation,
- mitral valve stenosis,
- idiopathic pulmonary hemosiderosis, a rare condition characterized by recurrent bleeding into the lungs,
- septic embolism resulting from right-sided heart endocarditis,
- pulmonary hypertension.
Other Causes
In some cases, severe nosebleeds, or bleeding originating from the mouth or throat, can result in blood appearing in the saliva during coughing, even though the true source of bleeding lies outside the lower respiratory tract. Blood can also result from certain medical procedures, including:
- lung biopsy,
- right heart catheterization,
- anticoagulant therapy (blood-thinning medications),
- thrombolytic therapy (clot-dissolving medications).
Additional conditions capable of causing hemoptysis include:
- chest trauma or pulmonary contusion,
- the presence of a foreign body lodged within the airway,
- coagulopathy (a disorder affecting the blood’s normal clotting ability),
- thrombocytopenia (an abnormally low platelet count, generally defined as below 150,000/mm³).
Diagnosis
Because hemoptysis is a symptom rather than a disease in itself, whenever a patient presents with blood coughed up alongside a fit of coughing, doctors must always investigate to identify the underlying cause. This thorough evaluation is essential because hemoptysis can, in some cases, represent the very first warning sign of a serious underlying condition, such as lung cancer or tuberculosis, making prompt and thorough investigation critically important.
The diagnostic workup to identify the cause of hemoptysis typically includes:
-
A detailed review of the patient’s medical history: The doctor will assess for a family history of conditions such as lung cancer, and will investigate whether the hemoptysis might be explained by a pre-existing medical condition already known to affect the patient.
-
Laboratory testing, which may include:
- markers of inflammation, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP),
- markers of infection, such as procalcitonin (PCT),
- coagulation studies, including prothrombin time (PT) and activated partial thromboplastin time (aPTT),
- a complete blood count, including platelet count.
-
Chest X-ray, often serving as the first-line imaging study to identify any obvious abnormalities within the lungs.
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Chest CT scan, which provides much more detailed imaging of the lungs and airways and is often essential for identifying the precise source and underlying cause of bleeding.
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Bronchoscopy: Since bronchoscopy is an invasive diagnostic procedure, it is generally reserved for cases in which all other diagnostic tests have failed to identify a clear cause, and the hemoptysis shows no signs of spontaneously resolving on its own. The situation is quite different in cases of massive hemoptysis, where bronchoscopy is typically used as the very first diagnostic and therapeutic approach, given that the patient’s life may be in immediate danger and a rapid diagnosis is essential. Bronchoscopy is considered the preferred first-choice intervention in cases of massive hemoptysis because it also allows doctors to directly suction blood from the patient’s airways, helping to prevent the serious risk of asphyxiation.
-
Testing for specific autoantibodies in the blood, including:
- c-ANCA,
- p-ANCA,
- ANA (antinuclear antibodies),
- anti-double-stranded DNA antibodies (ds-DNA-Ab).
This specialized autoantibody testing is performed in the relatively rare cases where doctors suspect that the hemoptysis might be related to an underlying vasculitis or another type of autoimmune condition affecting the blood vessels or lungs.
Treatment
The primary goal in managing a patient with hemoptysis is to first identify any immediate, life-threatening danger by carefully quantifying the volume of bleeding and assessing the patient’s overall oxygenation status.
The presence of any of the following symptoms alongside hemoptysis is a strong indicator of inadequate blood oxygenation and requires immediate medical attention:
- a bluish discoloration of the extremities or lips (cyanosis),
- difficult breathing (dyspnea) and an abnormally rapid breathing rate (tachypnea),
- disturbances of consciousness, including confusion, near-fainting sensations, or actual loss of consciousness.
In these situations, the patient requires prompt supplemental oxygen therapy, typically delivered via a face mask, and in more severe cases, may require intubation and mechanical ventilation to secure the airway and ensure adequate oxygen delivery to the body.
Once the patient’s immediate safety has been secured, several different treatment strategies may be employed depending on the severity and underlying cause of the hemoptysis.
Conservative Treatment
Mild to moderate hemoptysis can often be successfully managed through conservative treatment directed at the underlying condition responsible for the bleeding. Examples of conservative treatment include appropriately treating an underlying infection that has triggered the hemoptysis, or using anti-inflammatory medications in cases where an inflammatory condition is the root cause.
In these cases, the hemoptysis will typically resolve on its own gradually, as the underlying condition responsible for triggering the bleeding is successfully brought under control.
Bronchoscopy
A bronchoscope is a specialized medical device consisting of a flexible tube system that is inserted through the mouth and advanced into the main airways of the lungs.
This tool serves a dual purpose, both diagnostic and therapeutic:
- it allows doctors to directly visualize the inside of the airways, helping to precisely identify the source of the bleeding,
- it allows doctors to suction blood directly from the airways and, in some cases, to perform small procedural interventions aimed at achieving hemostasis (stopping the bleeding).
Bronchoscopy proves to be an extremely valuable tool in cases of massive hemoptysis, since it allows for the rapid removal of blood that would otherwise obstruct the airways, a situation that prevents air from reaching the lungs and places the patient at serious risk of death from asphyxiation.
Bronchial Artery Embolization (BAE)
Bronchial artery embolization (BAE) has recently become one of the most widely used and effective treatments for managing both massive and recurrent hemoptysis.
This is a non-surgical, minimally invasive interventional radiology procedure that works by selectively blocking specific blood vessels through the deliberate introduction of small embolic material (tiny particles or coils designed to occlude blood flow). By blocking blood flow to the specific area of the airway where the bleeding is originating, this procedure effectively stops the source of blood loss, leading to the resolution of the hemoptysis. BAE has become an increasingly preferred treatment option due to its relatively low invasiveness and high success rate in controlling even severe bleeding episodes.
Surgery
Given the potential for serious, life-threatening complications associated with surgical intervention, surgery should only be considered in cases where no viable alternative treatment strategies remain available. Currently, surgical treatment for hemoptysis remains indicated only in specific situations, including cases where the bleeding is caused by:
- lung cancer,
- complications arising from tuberculosis (such as cavitary tuberculosis),
- complex, treatment-resistant cases of aspergilloma,
- cases in which bronchial artery embolization has already been attempted without success,
- chest trauma resulting in significant lung damage.
Frequently Asked Questions
Is coughing up a small amount of blood always dangerous?
No, coughing up a very small amount of blood, particularly blood-streaked mucus following a prolonged bout of coughing or a mild respiratory infection, is common and usually not dangerous, especially in young, otherwise healthy individuals. However, any episode of coughing up blood should still be reported to your doctor, particularly if it recurs, persists, or is accompanied by other concerning symptoms such as weight loss or persistent fatigue.
What is the difference between hemoptysis and hematemesis?
Hemoptysis refers to blood originating from the lungs or airways that is coughed up, typically appearing bright red and frothy due to mixture with air. Hematemesis, on the other hand, refers to blood that is vomited up from the gastrointestinal tract, typically appearing darker in color, sometimes resembling coffee grounds, and often mixed with food particles. Both conditions can represent serious medical emergencies and warrant prompt evaluation, but they point toward very different underlying causes and require different diagnostic approaches.
Can anxiety or stress cause you to cough up blood?
No, anxiety and stress themselves do not directly cause hemoptysis. While stress can certainly worsen a chronic cough or contribute to hyperventilation, any actual blood appearing in coughed-up sputum always warrants a proper medical evaluation to rule out an underlying physical cause, since psychological stress alone cannot account for this symptom.
How much blood needs to be present for it to be considered an emergency?
While any amount of blood coughed up should prompt a conversation with your doctor, coughing up more than about one tablespoon of blood, or experiencing recurrent episodes, should be treated as urgent. Massive hemoptysis, generally defined as the loss of 500 milliliters or more of blood within 24 hours, constitutes a true medical emergency requiring immediate treatment in a hospital setting, given the significant risk of airway obstruction and asphyxiation.
Can lung cancer cause coughing up blood even in its early stages?
Yes, hemoptysis can occasionally be one of the earliest warning signs of lung cancer, even before other symptoms become apparent. This is precisely why any unexplained episode of coughing up blood, particularly in individuals with risk factors such as a significant smoking history, should be promptly and thoroughly investigated by a physician, even if the bleeding appears minor or occurs only once.
Sources and Bibliography
- Harrison’s Principles of Internal Medicine, 18th Edition. Milan: CEA Casa Editrice Ambrosiana, 2012.
- Earwood, J. S. & Thompson, T. D. Hemoptysis: Evaluation and Management. American Family Physician, 91, 243-249 (2015).
- Ittrich, H., Bockhorn, M., Klose, H. & Simon, M. The Diagnosis and Treatment of Hemoptysis. Deutsches Ärzteblatt International, 114, 371-381 (2017).
- American Thoracic Society: Patient Information Series - Hemoptysis
- Mayo Clinic: Coughing Up Blood
- National Health Service (NHS): Coughing Up Blood
