Seeing blood and mucus in your old dog’s stool is alarming and often a sign of an underlying health issue.
While occasional soft stool or digestive upset can happen, persistent bloody or slimy poop in senior dogs should never be ignored.
We outline the reasons why an old dog may be pooping blood and mucus, what you can do at home, and when to seek veterinary help.
Old Dog Pooping Blood and Mucus — Why It Happens
An old dog pooping blood and mucus usually means inflammation, infection, or irritation in the digestive tract. It can be linked to conditions like colitis, parasites, gastrointestinal infections, dietary indiscretion, or more serious illnesses such as cancer or organ disease.
Because older dogs have more fragile immune and digestive systems, even minor issues can become severe quickly. This is why prompt evaluation is so important when these symptoms appear.
Old Dog Pooping Blood and Mucus: Common Causes
Colitis
Colitis, or inflammation of the large intestine, is one of the most common causes of blood and mucus in an old dog’s stool.
The colon becomes irritated, leading to frequent attempts to defecate, small amounts of soft or liquid stool, and visible streaks of blood or slimy mucus.
Stress, dietary changes, or infections can trigger colitis, but in older dogs it may also signal a chronic condition like inflammatory bowel disease.
While colitis can sometimes resolve with dietary management, persistent cases require veterinary care to prevent dehydration and ongoing discomfort.
Read more: Old dog not eating and pooping blood (Here’s Why)
Gastrointestinal Infections
Bacterial, viral, or fungal infections in the digestive tract can cause bloody diarrhea with mucus. Senior dogs are especially vulnerable because their immune systems are weaker.
Infections may result from contaminated food, dirty water, or exposure to other sick animals. Signs often include fever, lethargy, loss of appetite, and abdominal pain along with abnormal stool.
Because dehydration and sepsis are real risks, infections should be taken very seriously in old dogs.
Intestinal Parasites
Worms and protozoa such as hookworms, whipworms, and giardia can cause an old dog to poop blood and mucus.
These parasites damage the intestinal lining, leading to irritation, inflammation, and in severe cases, anemia.
You may also notice weight loss, poor coat condition, or scooting behavior. Even if your dog has been dewormed before, reinfection can occur, and some parasites are not always detectable in a single stool sample. Regular vet checks and fecal exams are essential.
Dietary Indiscretion or Food Intolerance
Older dogs may develop sensitive stomachs and have a harder time digesting certain foods.
Eating spoiled food, table scraps, or foreign objects can irritate the digestive tract and cause bleeding and mucus in stool.
Food allergies or intolerances can also lead to chronic inflammation of the intestines. In these cases, the symptoms may appear gradually, with recurring bouts of soft stool mixed with blood or mucus. Identifying and eliminating the offending ingredient is key to long-term relief.
Cancer of the Digestive Tract
Unfortunately, bloody stools in senior dogs can sometimes indicate cancer, such as tumors in the colon or rectum.
These growths may bleed or interfere with normal digestion, leading to blood and mucus in the stool.
Other warning signs include weight loss, decreased appetite, straining to defecate, or visible lumps around the anus.
Because cancer is more common in older dogs, this possibility must be ruled out by a veterinarian if symptoms persist.
Anal Gland Problems
Anal glands, located near the rectum, can become infected, impacted, or even develop tumors. When this happens, blood and mucus may be seen in or around the stool.
Dogs with anal gland issues often scoot on the floor, lick excessively under their tail, or show signs of discomfort when sitting. Left untreated, anal gland infections can rupture and cause serious complications.
What to Do If Your Old Dog Is Pooping Blood and Mucus
If your old dog passes stool with blood and mucus, first remain calm but take the symptom seriously.
Ensure your dog stays hydrated by providing fresh water and consider offering a bland diet such as boiled chicken and rice to soothe the digestive system temporarily.
Monitor the stool closely. Note whether the blood is bright red (indicating lower digestive tract issues) or dark and tarry (pointing to bleeding higher up in the stomach or intestines). Keeping a stool sample for your vet can be very helpful.
Limit treats, table scraps, or sudden diet changes, as these can worsen irritation. If your dog is otherwise stable, short-term supportive care may help while you prepare for a vet visit.
But do not delay professional evaluation, especially in senior dogs, as their health can decline quickly.
When to Call or Visit Your Vet
You should call your vet promptly if your old dog:
Passes blood or mucus in stool more than once.
Shows signs of lethargy, vomiting, or loss of appetite.
Appears dehydrated, weak, or in pain.
Has dark, tarry stools that suggest internal bleeding.
Continues to strain or produces very little stool.
Because blood in the stool can range from mild irritation to life-threatening disease, it is always safest to have your veterinarian examine your senior dog. They may recommend fecal testing, bloodwork, X-rays, or an ultrasound to identify the cause.
Read more: Old Dog Poop Like Jelly With Blood (What it means)
Key Takeaway
When an old dog is pooping blood and mucus, it’s a clear signal that something is wrong in the digestive system. While mild colitis or dietary upset may resolve, more serious conditions like infections, parasites, or cancer require urgent attention.
At home, you can support your dog with hydration and bland foods, but veterinary care is essential for diagnosis and treatment. Quick action can make the difference between a manageable issue and a serious health crisis.
Caring for an aging dog means staying vigilant and responsive. By paying close attention to stool changes and acting promptly, you give your old dog the best chance for comfort, healing, and a good quality of life.