I start with a teaspoon, then increase if I feel necessary. It is good to adjust the amount based on your body size/weight, how you feel, results you see, etc. Every body is different. My friend's husband used the amount suggested on the bottle and had *major* diarrhea!
That's why I say start conservatively, then decrease or increase based on what happens.
I'm not sure why you'd be tired...unless maybe you're getting dehydrated???