My dog got sick after I changed her food.
It was my first year of veterinary school, and I started her on a diet to try and finally lose the extra weight she'd been carrying for too long. My dog loved food. The first red flag was when she had less appetite. "Well, it's a diet food," I thought. "She probably doesn't like it as much, or it's helping her stay full."
The second red flag was a loss of energy. My dog was older, 12 at the time. "Well, she's getting up there," I thought. "She isn't going to act like a puppy forever."
The third red flag was smaller, less frequent stools. Again, this was a new diet for weight loss. "It's higher in fiber," I thought. "That should cause bigger stools, more often, but maybe she's just adjusting."
Finally, my dog collapsed. It was a brief episode, she was back to herself afterwards, but I was out of reasons. That night, we drove to my old workplace back home and I had her seen.