I was enjoying taking Animal Pak, seemed to give me a boost of energy and made me feel better overall.. I quit taking the supplement and was only taking half dose (1 scoop) instead of full dose (2 scoops) and after about 3 weeks of taking it I stopped to see what happened and oh boy. Headaches, weird muscle aches and it almost felt like nicotine withdrawal. Irritable, restless, kinda light headed like the feeling when you haven't ate anything.. After feeling like this I wanted to test that it was supplement and so I took a dose and it went away, it's not caffeine withdrawal because I drink 6 cups of coffee a day.. During withdrawals I tested blood pressure, blood sugar and everything was normal. Definitely not a placebo effect since using the supplement eliminated the weird withdrawal symptoms of not taking it. Something makes me believe this stuff could encourage some Kidney stones too with how much vitamins and minerals you're taking at once. If you look into the product it has more than just vitamins it has things like CoQ10 and other stuff that can mess with your blood sugar/pressure and herbal type stuff that probably could be causing me a bad effect