Depending on what the problem is you are treating!
What did the doctor say?
Dosage can be anything between 1 scoop (17 grams, or 1 tablespoon) in 4oz fluids twice a day, to half a scoop in 8oz once a day, to even more or less than that...
My 4 year old takes 1/2 capful in 8 oz of liquid a day.. If you are using it on your own and not by a doctors orders, I would start out with 1/4 cap full in 8 oz liquid every day and if that doesnt work in a few days, Id up it to 1/2 cap