Vomiting blood could be caused by many things including a non-food item in your dog's system, which may have punctured your dog's stomach, Poisoning, ulcers, a blood disorder, and more. It could also be that your dog cut it's mouth and swallowed blood and is now vomiting it up. If an ulcer is to blame, you can give your dog some pepcid or Zantac. It sounds like you have already done this. Read about Pepcid dosages and usage information here:
Zantac can be given to a dog at .25 to 1mg per pound every 8-12 hours. Read about usage here:
Check your dog's mouth to see if he has a wound in his mouth or a tooth that’s bleeding. If it is not swallowed blood, or you know that your dog has had a bone or ingested a foreign object Iyou should have her seen by your vet as soon as possible.
You can read more about blood in vomit here:
If your dog is bleeding from other places as well, then I would suspect ingestion of rat poison. So be sure to check if there is bleeding from other orifices as well. Your vet can help with ingestion of rat poisoin as well.
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Since there have been recalls on certain foods, please check the following site to be sure the food your animals eat is not affected. If it is affected, contact your vet as soon as possible. Have your dog seen if they have any symptoms.