When you are at rest in a warm bed, arteries dilate and blood pressure tends to be low. When you stand up, your body elevates blood pressure to be sure your brain is perfused so you don’t black out. Getting out of bed in a cold room could cause an increase in pressure. How high does it get when you stand up? Does it then return to normal? Is your blood pressure cuff accurate? Discuss these questions with your doctor.

High BP in A.M. The Saturday Evening Post