Coughing up blood means that blood is coming from somewhere in your lungs or airways, and your body is expelling it through a cough. The medical term is hemoptysis. In most cases, the amount is small (blood-streaked mucus or a teaspoon of bright red blood), and the cause turns out to be something treatable like a chest infection or bronchitis. But because it can also signal serious conditions like lung cancer or tuberculosis, any episode of coughing up blood deserves medical attention.
What It Actually Looks Like
Blood that comes from the lungs typically looks bubbly or frothy and is mixed with mucus or saliva. It can appear pink, red, or rust-colored, and the amount is usually small. This is different from vomiting blood, which tends to come out in larger quantities, looks darker (sometimes like coffee grounds), and may contain bits of food. The distinction matters because vomited blood comes from the digestive tract, while coughed-up blood comes from the respiratory tract, and the two point to very different problems.
Sometimes the blood isn’t coming from the lungs at all. A nosebleed that drains down the back of the throat, bleeding gums, or a cut inside your mouth can all send blood into the airway and trigger a cough. Doctors call this pseudohemoptysis. If you recently had a nosebleed, dental work, or a sore throat with visible bleeding, that may explain what you’re seeing. Still, it’s worth confirming the source with a doctor rather than assuming.
Common Causes
The most frequent cause of coughing up blood is acute bronchitis, an infection of the large airways that irritates and inflames the lining enough to cause small amounts of bleeding. Upper and lower respiratory infections, including pneumonia, are also common culprits. In these cases, the bleeding usually stops once the infection clears.
Beyond infections, other causes include:
- Bronchiectasis: permanent widening and scarring of the airways, often from repeated infections, which makes the tissue fragile and prone to bleeding
- Lung cancer: tumors can erode into blood vessels in the lungs, particularly in people with a history of heavy smoking
- Tuberculosis: still one of the leading causes worldwide, though less common in the U.S. and Europe
- Pulmonary embolism: a blood clot that travels to the lungs, which can damage tissue and cause bleeding along with sudden shortness of breath and chest pain
- Blood thinners: anticoagulant medications increase bleeding risk throughout the body, including the lungs. In one study of lung cancer patients started on blood thinners, roughly 8% developed hemoptysis within six months, often in the first days of treatment
In up to 30% of cases, no specific cause is found even after testing. Doctors call this cryptogenic hemoptysis, and it generally has a good prognosis.
When It’s an Emergency
Small amounts of blood-streaked mucus during a bad cough are common and rarely dangerous on their own. What changes the picture is volume and context. Coughing up more than a few tablespoons of blood in 24 hours is considered serious. Doctors define “massive” hemoptysis as roughly 200 milliliters (about three-quarters of a cup) or more in a day, though some definitions set the threshold lower for people with existing lung disease. Massive hemoptysis is rare, but it’s a medical emergency because the bigger danger isn’t blood loss. It’s the risk of blood flooding the airways and making it impossible to breathe.
Seek emergency care if you’re coughing up blood and also experiencing any of the following: shortness of breath at rest, chest pain or back pain, dizziness or lightheadedness, blood that keeps coming with each cough, or blood in large enough amounts that it’s hard to tell from mucus. Unexplained weight loss, fatigue, or a history of heavy smoking alongside blood in the cough also raise concern for something more serious like lung cancer.
How Doctors Find the Cause
The first step is almost always a chest X-ray, which can reveal infections, masses, or fluid in the lungs. If the X-ray doesn’t provide a clear answer, or if the bleeding is significant, a CT scan of the chest with contrast dye is the next move. The contrast highlights blood vessels and can pinpoint where the bleeding is coming from. Both imaging approaches are considered standard and appropriate for initial evaluation.
In some cases, doctors will also perform a bronchoscopy, threading a thin, flexible camera through your nose or mouth and into the airways. This lets them see the source of bleeding directly and, if needed, take tissue samples. Blood tests, including clotting panels, help identify whether a bleeding disorder or medication is contributing to the problem.
How It’s Treated
Treatment depends entirely on the cause. If a chest infection is responsible, antibiotics or antiviral medications typically resolve the bleeding along with the infection. If a blood-thinning medication is the trigger, your doctor may adjust the dose or switch to a different drug.
For more serious or persistent bleeding, a procedure called bronchial artery embolization is one of the most effective options. A specialist threads a thin catheter through a blood vessel (usually starting in the groin) and navigates to the artery feeding the bleeding site in the lung. Tiny particles are then injected to block that artery and stop the bleeding. This procedure has an immediate success rate of over 99%, according to a large systematic review. However, about 24% of patients experience some recurrence of bleeding over time, and the overall complication rate is around 13%, with the vast majority being minor (temporary chest discomfort or difficulty swallowing).
For bleeding caused by lung cancer, treatment targets the tumor itself through surgery, radiation, or chemotherapy. In cases of pulmonary embolism, blood clot treatment with anticoagulants addresses the underlying problem. When massive hemoptysis occurs, patients are stabilized in an intensive care unit first, with the priority being to protect the airway and maintain breathing before any diagnostic testing begins.
What to Pay Attention To
If you’ve coughed up a small amount of blood once during a cold or bad cough and it doesn’t happen again, the cause is likely minor irritation of the airways. Keep track of whether it recurs, and mention it to your doctor at your next visit.
If the bleeding happens more than once, increases in amount, or comes with no obvious explanation like a respiratory infection, schedule an appointment soon rather than waiting. Note the color (bright red, dark red, rust-colored, or pink), the approximate amount, and whether it was mixed with mucus. This information helps your doctor decide how urgently to investigate and which tests to order first.