Is it normal...

...that my vet has never taken my dog's blood? They take a stool sample and do a physical check, but she's never been given any type of blood test or received any sort of body scan. She's a rescue and we've been seeing this vet for two years.

Why I ask:

Last month we had to take her into the vet because she was having blood in her stool. We gave a stool sample, and were told it came back negative, she was fine. Now it's happening again a month later. Again, we took her in, gave a stool sample, and have been told she's fine. Given that this is the second time it's happening, I'm nervous about her health and I wonder if this is the normal/best practice for vets or if we should be seeing someone else.

Thanks!