If your dog is coughing up blood clots, it is an alarming and urgent sign that something serious is affecting their lungs, throat, or internal organs.
Even small clots indicate that bleeding inside the respiratory tract has progressed beyond mild irritation.
We outline the common causes of a dog coughing up blood clots, what you can do, and when to seek veterinary help.
Dog Coughing Up Blood Clots — Why It Happens
A dog coughing up blood clots is most often experiencing severe airway inflammation, lung disease, trauma, infection, heart failure, blood-clotting disorders, or internal bleeding that has reached a critical point.
Unlike mild blood-streaked mucus, blood clots form when bleeding has been ongoing or intense.
Dog Coughing Up Blood Clots: Common Causes
Severe Respiratory Infections
Advanced infections can damage the delicate tissues inside the lungs and airways. As inflammation worsens, blood vessels become fragile and may rupture during coughing. This can lead to thick, dark red blood clots being expelled with mucus.
Dogs with severe infection may also show fever, lethargy, fast breathing, weakness, nasal discharge, or a wet cough. When pneumonia progresses, the lungs fill with inflammatory fluid, and the dog may cough forcefully to clear it.
The constant strain tears fragile airway tissues, allowing internal bleeding to pool and form clots.
This level of respiratory irritation is serious because it indicates that inflammation is deep and extensive. Without treatment, oxygen levels can drop, leading to respiratory failure.
Read more: Dog Coughing Up White Foamy Mucus (Explained)
Heart Disease or Congestive Heart Failure
Heart disease can cause fluid buildup in the lungs, known as pulmonary edema. When fluid overwhelms the airways, coughing becomes more aggressive and frequent.
Over time, the pressure and strain can rupture lung vessels, causing bleeding that forms clots.
Dogs with heart disease often cough more at night, breathe rapidly, or collapse after exercise. As the heart weakens, blood backs up into the lungs, causing swelling and irritation that leads to clot formation.
Coughing up blood clots in a dog with known heart disease is a medical emergency because it may signal worsening heart failure or lung hemorrhage.
Trauma or Injury to the Chest or Airway
Any physical trauma — from being hit, falling, choking on a toy, or even pulling too hard on a collar — can injure the throat or lungs. Internal bruising can cause blood to pool inside the airways, forming thick clots that appear during coughing.
Dogs may cough suddenly after the injury, swallow excessively, or breathe rapidly. Even minor trauma can cause significant internal damage because the airway tissues are extremely delicate.
Trauma-related clot coughing becomes more dangerous because swelling or airway blockage may follow.
Foreign Object in the Airway
A grass awn, seed, piece of food, or small toy part lodged inside the airway can cause severe inflammation and bleeding. Dogs may cough violently as their body attempts to remove the object.
When the irritation is deep within the lung, blood may pool around the site of injury, forming clots. Foreign objects often cause sudden onset coughing, gagging, or panic, but if lodged deeper, symptoms may be more gradual. As the object moves or causes infection, clot-based coughing worsens.
This is an emergency because foreign objects can migrate into lung tissue and cause long-term damage.
Lung Tumors, Masses, or Cancer
Lung cancers or masses inside the chest cavity can rupture fragile blood vessels as they grow. Dogs may cough up recurring blood clots as the mass irritates the surrounding tissues.
Tumor-related coughing often appears gradually, worsening over weeks. Dogs may lose weight, breathe heavily, fatigue quickly, or show reduced stamina.
When clots appear, it usually means internal bleeding has increased. Bleeding in the lungs is serious and requires immediate diagnostic imaging.
Blood-Clotting Disorders
Some dogs have conditions that affect how their blood clots. This may be due to internal disease, toxins (such as rat poison), autoimmune disorders, or inherited clotting problems.
When blood does not clot normally, even mild airway irritation can result in large internal bleeds. Dogs may cough up dark red or jelly-like clots and show other signs such as bruising, nosebleeds, or pale gums.
Because clotting disorders cause widespread internal issues, dogs can worsen rapidly without treatment.
Severe Allergic Reactions or Irritation
Though rare, extreme airway inflammation from severe allergic reactions can damage blood vessels enough to cause bleeding. Dogs may cough suddenly, choke, gag, or wheeze before producing blood-tinged clots.
Allergic airway reactions are more likely in dogs exposed to harsh chemicals, insect stings, or strong inhaled irritants.
While this cause is uncommon, clot formation indicates severe inflammation that must be addressed quickly.
Lungworm or Parasitic Infections
Certain lung parasites damage lung tissue as they migrate through it. The irritation can lead to coughing that produces mucus, foam, or even blood clots in advanced cases.
Dogs may show reduced stamina, weight loss, or persistent coughing. Parasitic irritation becomes serious because internal bleeding accumulates over time, creating larger clots.
Read more: Dog Coughing Up Phlegm With Blood (What it means)
What to Do If Your Dog Is Dog Coughing Up Blood Clots
Move your dog to a calm, quiet space and restrict movement immediately. Physical activity increases coughing, which can worsen internal bleeding. Observe your dog’s breathing rate and look for signs of distress such as fast breathing, open-mouth breathing, or pale gums.
Do not offer food until vomiting or coughing settles. Offer small amounts of water only if your dog is fully alert. Avoid giving any human medications — many worsen bleeding or respiratory distress.
Look at the clots if possible: bright red indicates fresh airway bleeding, while dark clots suggest older, deeper bleeding. This information helps your veterinarian understand the severity.
Any amount of clot-based coughing warrants urgent evaluation. Avoid delaying care, as internal bleeding can escalate quickly.
When to Call or Visit Your Vet
Seek emergency veterinary care immediately if your dog is coughing up blood clots. This symptom is always serious, especially if accompanied by:
• Rapid, shallow, or labored breathing
• Weakness, collapse, or lethargy
• Pale, gray, or blue gums
• Vomiting blood or passing blood in stool
• Refusal to eat or drink
• Fever, shaking, or sudden weight loss
• Gagging, choking, or signs of obstruction
• A history of heart disease, trauma, or toxin exposure
X-rays, blood tests, ultrasound, and airway exams are often needed to identify the source of bleeding and start treatment quickly.
Read more: Dog Coughing and Hacking Suddenly (Sudden airway irritation explained)
Key Takeaway
A dog coughing up blood clots is experiencing severe airway irritation, lung disease, heart failure, trauma, parasites, or bleeding disorders.
While occasional coughing may be harmless, coughing up clots is always a red flag that requires immediate veterinary evaluation.
With quick action and proper treatment, many underlying causes can be managed, helping your dog breathe more comfortably and recover safely.