If you have high blood pressure it means your heart is working much harder to pump blood throughout the body and jumping into a fitness program without considering your BP, and without the supervision of a fitness professional, can be dangerous.
For instance, pushing your body too hard or holding your breath while performing lifts (a common reaction) can dramatically increase your BP which increases your risk of a heart attack or stroke.
While there is no cure for high blood pressure, it can be managed. It’s important to talk to your doctor before starting a new fitness program.