What are the issues or side effects for eating grapefruit while taking blood pressure medicine?

Depends on the med.: Grapefruit can interact with some medications, but certainly not all. You don't say what meds you take. It can also interact with statin drugs that lower cholesterol and with other meds too. Here's a page all about grapefruit! Hopefully you are not on one of those meds and can enjoy a great fruit! https://www.rxlist.com/grapefruit/supplements.htm