I am 15 weeks pregnant & I was wondering if grapefruit juice is safe to drink?

Fruit is excellent. Eating fruit (and vegetables) as part of a balanced diet is excellent for a pregnant woman. Juice is an option also, especially if craving a fruit that is out of season. Having a nutritionist or physician go over the important nutrients is helpful. You could also visit my guide to healthy eating; the link is provided in the comments.