These symptoms could be indicative of a serious medical condition, and a vet can properly diagnose the cause and provide the appropriate treatment.
Here are some possible reasons why your dog might be experiencing these symptoms, but it's crucial to remember that this is not an exhaustive list and should not be used to self-diagnose your dog:
Possible Causes of Vomiting Blood and Loss of Appetite:
* Gastrointestinal issues: Gastritis, ulcers, parasites, inflammatory bowel disease, foreign object ingestion
* Liver problems: Liver disease, hepatitis
* Kidney problems: Kidney failure
* Pancreatitis: Inflammation of the pancreas
* Poisoning: Ingestion of toxins, medications
* Trauma: Internal bleeding due to injury
* Cancer: Tumors in the gastrointestinal tract
* Infectious diseases: Parvovirus, distemper
Do not delay seeking professional veterinary care. The sooner you get your dog to the vet, the better the chances of a successful diagnosis and treatment.