As with anything, to much of a good thing can be bad. Lets look at water, delicious and necessary for all life on earth but too much is called drowning. Any supplement can be bad if way too much is taken, AKA abused. When prohormones are taken as recommended they are safe, or the FDA wouldn’t allow you to buy them at the store or off of this website. Just to make sure, I have ran human trials and found the products by AMS to be safe. I don’t know the exact compounds, because it was a double blind prospective human trial: the highest level of human study.
Many advanced users stack several compounds in order to get maximum results from their cycle. Normally when your stacking these types of supplements its best to use single compounds instead of premixed stacks. The problem with using a premixed stack is you may get more of one compound than you want. Most of these products have sweet spots. Lets use h-drol for an example according to many of the forums out there 75mg is the sweet spot for this compound. Now lets say you have a halodrol product that is mixed with 10mg of Methylstenbolone. In order to get the proper amound of hdrol you will get more than the recommended dose of M-sten.