Blood in your mucus when you cough is usually caused by an infection, most commonly bronchitis or pneumonia. A few streaks or flecks of blood in your phlegm can look alarming, but in most cases the cause is minor and treatable. That said, blood in your mucus always deserves attention because it can occasionally signal something more serious.
The Most Common Causes
Infections are the leading reason people see blood-tinged mucus. When your airways are inflamed from an illness, the small blood vessels lining your throat and bronchial tubes become irritated and fragile. Repeated forceful coughing can rupture these tiny vessels, mixing blood into your phlegm.
Bronchitis is the most frequent culprit. During a bad chest cold, the lining of your airways swells and produces excess mucus. Days of hard coughing can irritate that lining enough to cause small amounts of bleeding. The blood typically appears as streaks or pink-tinged mucus rather than large amounts, and it resolves as the infection clears.
Pneumonia can also produce bloody or rust-colored sputum, along with fever, chest pain, and shortness of breath. The infection inflames the air sacs deep in the lungs, and the combination of inflammation and coughing leads to blood mixing into what you cough up. Bacterial pneumonia is treated with antibiotics, and the bloody mucus stops once the infection is under control.
Other Reasons Blood Shows Up
Not every case traces back to a chest infection. Several other conditions can cause blood in your mucus:
- Nosebleeds or sinus infections. Blood from your nasal passages can drain down the back of your throat, especially at night, and mix with mucus you cough up in the morning. This is sometimes called pseudohemoptysis because the blood isn’t actually coming from your lungs. A doctor will examine your mouth and nasal passages to rule this out.
- Bronchiectasis. This is a chronic condition where the airways become permanently widened and damaged, making them prone to repeated infections and bleeding. People with bronchiectasis often cough up mucus daily and may notice blood during flare-ups.
- Blood thinners. If you take anticoagulant medications, even mild airway irritation can produce noticeable bleeding that wouldn’t occur otherwise.
- Severe or prolonged coughing. Sometimes there’s no underlying disease at all. Violent coughing fits, from any cause, can simply tear small blood vessels in your throat or airways.
When Blood in Mucus Could Be Serious
Lung cancer can cause blood or rust-colored sputum, and it’s one of the most common symptoms that leads to diagnosis. This is more likely if you’re over 40, have a history of smoking, and the bloody mucus persists for weeks without an obvious infection. Other warning signs include unexplained weight loss, a cough that won’t go away, and recurring chest infections.
Tuberculosis produces a persistent cough lasting three weeks or longer, often with blood-streaked sputum, chest pain, night sweats, and fever. TB is less common in many developed countries but remains a serious global health concern, and it requires specific testing to diagnose.
A pulmonary embolism, a blood clot that travels to the lungs, can also cause you to cough up blood. The hallmark symptoms are sudden shortness of breath that appears even at rest, sharp chest pain that worsens when you breathe in deeply, and a rapid heartbeat. This is a medical emergency.
How Much Blood Matters
The amount of blood you see is one of the most important details. A few streaks or flecks mixed into your mucus is very different from coughing up pure blood or large clots.
Clinicians consider it life-threatening when someone coughs up roughly half a cup (about 150 mL) of blood within 24 hours, or when bleeding reaches about 100 mL per hour. That volume is unmistakable. You would not confuse it with a few pink streaks in your tissue.
Even small amounts warrant a call to your doctor if they persist for more than a few days, happen without an obvious cold or chest infection, or are accompanied by fever, weight loss, shortness of breath, or chest pain. If you’re coughing up more than a few spots and having difficulty breathing, a racing heartbeat, or pain in your chest or upper back, that calls for emergency care.
What Happens at the Doctor’s Office
The first step is confirming that the blood is actually coming from your lungs and airways rather than your nose, mouth, or stomach. Your doctor will examine your oral cavity and nasal passages. Sometimes distinguishing between these sources requires a scope passed through the nose or down the throat.
A chest X-ray is standard for anyone coughing up blood. It can reveal pneumonia, masses, or other abnormalities in the lungs. If the X-ray doesn’t explain the bleeding, the next step is typically a CT scan with contrast dye, which gives a much more detailed picture and is better at pinpointing the cause.
Bronchoscopy, where a thin camera is threaded into the airways, is sometimes used as well. It’s particularly useful for spotting growths or lesions inside the bronchial tubes and can collect tissue samples or stop active bleeding at the same time. Blood tests may also be ordered to check for clotting problems that could be contributing to the bleeding.
How It’s Treated
Treatment depends entirely on the underlying cause. For bronchitis, the answer is often rest, fluids, and time. Bacterial pneumonia calls for antibiotics. TB requires a specific multi-drug treatment regimen that lasts several months. If the cause is a blood clot in the lungs, treatment focuses on dissolving or managing the clot.
When a tumor is responsible, the path forward involves surgery, radiation, or other cancer-directed therapies depending on the type and stage. For bronchiectasis, treatment centers on managing infections and keeping the airways clear to reduce flare-ups.
In cases of severe or persistent bleeding from the airways, a procedure called embolization can be used to block the blood vessel that’s causing the problem. This is reserved for situations where the bleeding is heavy or doesn’t respond to treatment of the underlying condition.
For most people, the blood in their mucus turns out to be a byproduct of a respiratory infection and clears up within days to a couple of weeks. The key is paying attention to how much blood you see, how long it lasts, and whether other symptoms are present alongside it.