It’s not completely harmless, for me it causes heart palpitations that are so bad my watch tells me I’m in atrial fibrillation. Yes I know this sounds crazy. I’ve ruled everything else out. No, it is not creatine mixed with caffeine or whatever. Just pure creatine. No, I don’t have any other heart issues. I can give myself an irregular heartbeat just by having some creatine. It doesn’t happen otherwise. I have seen a cardiologist, he said it’s rare but it is theoretically possible.