Friend, when a dog is vomiting blood this could the result of disorders affecting the gastrointestinal tract or secondary to a systemic disease. It will be difficult for me to determine the exact underlying cause without a hands on examination and some testing. But, common causes are: Ulcers, ingestion of a foreign body, infections, tumors, kidney or liver disease, toxicity, etc. to name a few causes. The other concern is her gums being pale; this could be a sign of: Anemia, poor circulation, blood shifting, decrease blood pressure or cardiac output, etc. Dogs that go untreated with pale gums could have a fatal outcome.
Unfortunately we are somewhat limited as to what you can do at home. I would strongly recommend having her checked tonight by ER veterinarian for supportive care. In addition, the attending veterinarian will be able to run some test to try to determine the cause of the vomiting with blood. If you do not have access to ER vet this is what you can do until she is seen in the morning by family veterinarian:
1- Do not give things like Pepto Bismol or imodium. Start her on Pepcid AC (famotidine) 10mg tablet every 12 hours. You can buy Pepcid AC over the counter in any pharmacy.
2- No food or water for 6-8 hours. Need to give her gastrointestinal tract time to rest.
3- After 6-8 hours offer a small amount of water. Wait half hour, if no vomiting, continue giving her water in small amount every hour or so. Leave her without food until she is seen by vet in the morning.
4- Follow up with your family veterinarian for a hands on examination in the morning.
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