If your pet is experiencing diarrhea it is important that the nature and severity of the problem is reviewed with a veterinarian. When your pet is under the care of a veterinarian for a known condition that includes diarrhea as a symptom it may still be recommended that you seek veterinary assistance in many cases.
Blood in the stool is an indication of a potentially serious issue. Blood might be black or dark and sticky or odorous. It may not look to you to be blood but if it's very dark or tacky it might be blood. Bring your pet to his primary veterinarian if they are open or to the emergency room any time of the day or night.
The severity of the amount of diarrhea excreted or the number of times your pet has eliminated diarrhea is also important when considering the severity of the problem. Pets can dehydrate very quickly when they have diarrhea and veterinary intervention is needed to measure what is happening to your pet as a result of the ongoing diarrhea. Even if it seems to have cleared up, there's no way to know if your pet has lost vital nutrients without an examination.
Diarrhea accompanied by fever, vomiting or lethargy indicates that your pet is sick and that veterinary care is needed. Please call your local veterinarian or bring him to the emergency hospital for evaluation and treatment.