Depends if you have the powder or tablets. If you have the powder type , 5-10 mins before you eat as it will hit you fast and you can feel it ( i'll mix the correct ammount in a small cup of water and drink it like a shot) . If you have tablets, take into account the time the gelcap needs to dissolve first so about 20 mins or more before your meal. Hope this helps out. -scrh1