Is pre workout supplements bad for people who have had a bloodclot?

Depends: Since the supplement industry is not regulated by the fda, the ingredients in supplements do not necessary have to contain what it claims or more so may have other ingredients not listed. With that said, having a blood clot does preclude you from having supplements that can affect your clotting ability, such as vitamin k. If you had a clot in the past, it is important to consult your physician.