What Causes Dizziness And Tiredness While Having BP?

Hi my husbands blood pressure is 70/47. We were just at our doctor s office a couple of days ago and he didn t say to stop taking the blood pressure medicine - lysinopril 20mg and hydrochlorithiazide 12.5mg. He just came in from working outside and complained of dizziness and we took his bloodpressure. He s frequently complaining of being tired. He s 73 yrs old. Thanks