You have to play the odds. If you take a supplement that you buy at a dollar store, the odds are not in your favor. (That stuff more often than not is made in China.)
Interestingly, one of the most dangerous drugs is Tylenol. Taking two of them puts you very close to a dangerous dose. Thus, if you also take another drug, just after taking Tylenol, which contains the main ingredient in the latter, you stand an excellent chance of losing your liver.