[header] How to treat a cat with blood in its stool [title] Talk to your veterinarian asap. [step] As soon as you notice blood in your cat's stool, make a call to your vet. Tell them what you saw in your cat's litterbox and ask them to make you an appointment.
Most vets will take these symptoms very seriously and will try to get you in very quickly. Ask them for any advice as to how to care for your cat in the meantime.