I have a 1 year old yorkie! She has been pooping blood.. Almost like tar! She seems to only do when she eats something otger than her dog biscuits and Iams dog food. What should I do?

You shouldn't wait for an answer here, but take her to the vet immediately. Does she have a habit of chewing on hard objects, plastics, wood, etc. She could have something lodged in her intestines.

Yes, you take it to your vet ASAP.

If she is pooping blood when you feed her things other than dog food and dog biscuits, than I would suggest to stop feeding her other things.

Lots of things can cause blood in the stool from parasites such as hookworms and whipworms, to obstructions of the stomach and/or intestines to excessive diarrhea.

If my dog were having bloody BMs continuously, I would be taking her in as soon as possible. I would probably also suggest to hold her off food until you can get her into a vet sometime tomorrow.