Grapefruit juice, I hate the stuff. But did you know that if you drink as little as 8 oz. of it when you take certain medications it could dramatically increase the effectiveness of the medicine? Sounds like a great thing, sure, until you realize that the dose of medication you are taking is specific to you and that increasing it can have serious side effects and in some cases cause death. This discovery led to the inclusion on the labels of certain medications to be cautions about grapefruit juice [and grapefruit] consumption.