Seeing your dog hacking up blood is frightening. Blood in a dog’s cough can range from a minor irritation to a sign of a very serious medical condition, which makes it important to understand what may be happening.
We outline the common causes of a dog hacking up blood, what you can do at home, and when to seek veterinary help.
Dog Hacking Up Blood: Why It Happens
A dog hacking up blood usually happens when there is irritation, inflammation, infection, trauma, or bleeding somewhere in the respiratory tract, mouth, throat, or even the digestive system. The blood can come from something as simple as a ruptured nasal vessel during a forceful cough, or from more serious issues like pneumonia, foreign bodies, or internal bleeding.
Some dogs hack up blood because of severe bronchitis, heartworm disease, kennel cough complications, or ingested toxins.
Others may have bleeding disorders or cancers that cause fragile tissues to rupture during coughing.
Dog Hacking Up Blood: Common Causes
Respiratory Infections
Respiratory infections are among the most common reasons for a dog hacking up blood. When the airways become inflamed, the lining of the trachea and bronchi becomes fragile.
Forceful coughing can irritate these already sensitive tissues, causing small blood vessels to break and leading to streaks or droplets of blood in the mucus your dog hacks up.
Dogs with pneumonia may produce thick mucus mixed with blood, especially when the infection is advanced.
Kennel cough, while usually mild, can become severe and lead to violent coughing episodes that cause bleeding. Bronchitis makes the airways chronically inflamed, leaving them more prone to bleeding even with lighter coughs.
Other symptoms may include wheezing, fever, nasal discharge, or lethargy. Because infections involving blood in the cough indicate significant airway irritation, timely veterinary care is important to prevent complications.
Read more: Dog Constant Hacking Cough (When to worry)
Foreign Body in the Throat
A foreign body lodged in a dog’s throat or airways is a serious and sometimes life-threatening cause of hacking up blood. Objects like grass seeds, splinters, bone fragments, or small toys can scrape or puncture delicate tissues.
When your dog coughs to try to dislodge the object, the friction causes bleeding that appears as blood-tinged mucus or even bright red droplets.
Some dogs may gulp repeatedly, gag, swallow excessively, or paw at their mouth. Others may suddenly develop a deep, hacking cough that doesn’t improve.
Because foreign objects can migrate deeper into the chest and cause infection, abscesses, or airway collapse, this situation needs urgent veterinary evaluation.
Bleeding in the Mouth, Nose, or Throat
Not all blood that comes out during coughing originates from the lungs. Dogs may have bleeding gums, oral ulcers, dental infections, or nosebleeds that drip backward into the throat.
When they cough or gag, this swallowed blood is brought back up and looks like it is coming from the chest.
Nasal infections or fungal diseases may also cause significant bleeding. Dogs with chronic sneezing or reverse sneezing may rupture nasal vessels that ooze into the throat.
Dental disease can cause gum tissues to bleed during chewing or coughing, and that blood may be expelled during a hacking episode.
If your dog is coughing up blood along with drooling, bad breath, sneezing, or nasal discharge, the source may be upper rather than lower airway-related.
Heartworm Disease
Heartworm disease can lead to coughing that is severe, frequent, and progressively damaging to the lungs. Over time, the inflammation caused by the worms can scar lung tissue and make the surrounding blood vessels fragile.
When a dog with heartworms coughs, these weakened vessels can rupture, causing bloody mucus to appear.
Some dogs develop pulmonary hypertension—high blood pressure in the lungs—which further increases the risk of bleeding during coughing.
In advanced heartworm cases, hacking up blood can signal a dangerous complication called caval syndrome, where worms obstruct major blood vessels.
Even heart conditions unrelated to heartworms can cause fluid buildup or bleeding in the lungs, making coughing episodes more violent and more likely to produce blood.
Read more: Dog Hacking Up Yellow Foam (Causes and solutions)
Ingested Toxins
Certain toxins—such as rat poison (anticoagulants), some human medications, and toxic plants—can interfere with your dog’s ability to clot blood. When clotting fails, even minor airway irritation can produce significant bleeding.
Dogs may cough up blood because the blood vessels in their lungs or throat are leaking. In more advanced poisoning, dogs may also bruise easily, bleed from their gums or nose, or develop internal bleeding that causes pale gums and weakness.
Because toxin-related bleeding worsens over time, coughing up blood after possible exposure should always be treated as an emergency.
Cancer
Tumors in the respiratory system can cause a chronic cough that produces blood, especially when the tumor grows large enough to disrupt surrounding tissues.
Lung cancer may cause recurring episodes of hacking up blood-tinged mucus. Throat or nasal cancers may bleed spontaneously or during coughing fits.
These cancers may progress slowly or quickly depending on the type. Additional symptoms might include weight loss, lethargy, shortness of breath, noisy breathing, or decreased stamina. Because cancers often bleed easily, even mild coughing can lead to visible blood.
Any dog with unexplained coughing up blood—especially middle-aged or older dogs—should be evaluated for possible tumors.
Related: Dog coughing up white foamy mucus (What it means)
What to Do If Your Dog Is Hacking Up Blood
When you see blood in your dog’s cough, try to stay calm while assessing your dog’s overall condition. Begin by checking whether your dog is breathing comfortably. If the breathing seems labored or unusually fast, avoid stressing your dog and contact your veterinarian immediately.
Give your dog a quiet, calm space to rest. Reduce activity because coughing can worsen when a dog becomes excited or overexerted. If your dog was recently on a walk or playing when the coughing began, bring them indoors and allow the airways to settle.
Avoid giving human medications because many are toxic to dogs and can worsen breathing issues or bleeding. If you suspect your dog swallowed something sharp or irritating, do not attempt to remove it at home. Sharp objects can cause severe damage when handled incorrectly.
Monitor how much blood is present. Small streaks of blood mixed with mucus are less concerning than bright red gushes, but any recurring bleeding should be assessed by a vet.
Also note other symptoms such as lethargy, fever, nasal discharge, vomiting, or pale gums. These clues help your veterinarian identify the underlying cause quickly.
When to Call or Visit Your Vet
You should contact a veterinarian right away if your dog:
Produces more than a trace amount of blood.
Has difficulty breathing or rapid breathing.
Coughs continuously for several hours.
Shows pale gums or signs of internal bleeding.
Swallowed a foreign object.
May have been exposed to rat poison or other toxins.
Acts lethargic, weak, or collapses.
Seek emergency care immediately if there is bright red blood, large amounts of blood, or sudden worsening of breathing.
These are signs of conditions that cannot wait for a routine appointment.
Read more: Dog Hacking Up White Mucus (What it means)
Key Takeaway
A dog hacking up blood is always a symptom that deserves attention, even if the bleeding seems minor.
While some causes are treatable and mild, others involve infections, foreign bodies, toxins, or serious respiratory diseases that require prompt veterinary care.
Trust your instincts—if something feels off, it’s safer to have your dog checked quickly. With timely evaluation and the right treatment, many dogs recover well and return to breathing comfortably again.