Bloody stools in cats can be attributable to a variety of underlying causes. While red blood in small quantities, sometimes mixed with mucous, is fairly common in cats, it is always best to consult your veterinarian to pursue a diagnosis.
Some things to consider:
1. Blood in a cat's stool can often times be indicative of the cat having ingested Warfarin which is used in mouse and rat poison. If you suspect this is the case, take your cat to the Vet immediately. Depression is generally evident when a cat ingests enough of the toxin to cause bleeding.
2. Is the cat on a medication which may be the cause.
3. Dietary - Blood in a cat's stool is not uncommon when bowel movements are hard or dry, which may be attributable diet. Consider changing to a low fat/moderate fiber food or one that is highly digestible.
Other possible causes of blood in the stool:
1.Some bacterial infections can lead to blood in the stool. Clostridia, Salmonella, E. coli are a few of the bacterial infections associated with bloody stools.
2.Intestinal parasites, including worms, can lead to bloody stools in cats. Tapeworms will not show up in a fecal examination, but egg cases are passed and look like small grains of rice when they dry and can usually be found in the pet's fur. Hookworms and roundworms will show up in a fecal exam. Roundworms can encyst in body tissues and reinfect a cat throughout its lifetime, so they may be present even if they aren't found in a fecal exam. De-worm according to your vet's advice or the prescribed dose on the product.
Consult your veterinarian if there is a sudden onset of bloody stools and seek a diagnosis for the problem.