Is eating tumeric in excess bad?

Can be! Can't answer it without knowing how much. It is not poisonous but too much will give you a stomach ache and cramping with diarrhea.
Also. 1) not wise in pregnancy as can cause uterus to cramp 2) can increase bleeding if on blood thinners already. You may also bleed more easily even if not on blood thinners but you would have to take a very large dose. Don't take w/in 2 weeks of a surgery 3) some forms of chemotherapy don't work as well if tumeric is on board--check with your doctor. 4) can worsen gallbladder issues like gallstones.
What excess? Can't answer it without knowing how much. It is not poisonous but too much will give you a stomach ache and cramping with diarrhea.