What can happen if your blood pressure is too high?!

he can have a stroke.
But.....he needs to relax for about 5 10 minutes and then take his blood pressure again.
IT is not always accurate when taken the first time.
Also, some home devices are not all that accurate.
Is it something or a brand of device his doctor recommended or did he just buy it because he wanted one?
There are medications to lower his blood pressure and some diet hints, most to cut back on salt a lot will help.

High blood pressure or hypertension is referred to as “the silent killer”.
Over time, it can lead to damage of the heart and blood vessels, leading to stroke, heart attack or renal failure.

highbloodpressure.about.com