My fiance takes lisinopril 20mg daily is blood pressure still is high 185/125. why is his diastolic pressue so high?

Needs more BP medica: High blood pressure (hypertension) is very common. In most cases there is no specific cause. Such cases are called "essential hypertension". Very often, people who have high BP require 2 or 3 or even 4 medications to control it. In some cases, there is a specific cause like kidney disease or a hormonal or vascular problem. Your doctor will add medications and if necessary investigate further.