Has your dog every gotten seriously ill from vaccines or flea/heartworm meds? Long and some TMI

[devmer]

I haven't read all of the replies but you may want to look into addison's disease. My dog, the one in my profile pic, was recently diagnosed with this and your post sounds similar to what my dog did. She all of a sudden got super lethargic, vomited, and stopped eating. She didn't have diarrhea. We took her to the vet 3 times in 4 days. They thought it was a gastro thing too and gave us a ton of meds that didn't help. The 3rd time we took her in we had a different doctor and he guessed addisons. She was so dehydrated we had to take her to an emergency vet, since ours wasn't a 24hour one, and she had to stay overnight for fluids. While she was there they tested her for addisons and it came back positive. She is now on prednisone for the rest of her life, she also needs a steroid shot every 25-30 days. If she is not getting better it could be addisons. It is pretty rare but is more common in young to middle aged females.