“Should I go to the ER for bloody diarrhea?”

Reasons to seek care in the ED would include progressive worsening bleeding, significant and progressive abdominal pain, high fever, signs of dehydration, history of inflammatory bowel disease or history of colorectal cancer. Age isn't specified here, but an infant or toddler with blood in the stool should be evaluated for a condition called intussusception. If you suspect that this is a foodborne illness, an evaluation with a primary care or urgent care provider would often start with a stool culture to evaluate for infectious causes.

Yes, if it does not resolve or you have dehydration or anemia.