Harvard Heart Letter

Ask the doctor: Should I worry about low nighttime blood pressure?

Q. My systolic blood pressure is high in the morning (about 165), but in the evening it drops to below 100. I am taking two blood pressure medications daily and still experiencing seriously low blood pressure at night. What would you suggest?

A. Everyone's blood pressure changes throughout the day, and it's often highest in the morning and lowest at night. You seem worried about the low pressure at night, but that would concern me only if it's accompanied by symptoms such as dizziness or fainting. A systolic (top number) pressure below the normal of 120 is usually not worrisome. In fact, studies show that low blood pressure while you are sleeping predicts low cardiovascular risk.

I'm more concerned about your high morning pressure and the big difference between night and morning. Getting out of bed in the morning leads to a surge in adrenaline, and this is something you can't prevent — unless you stay in bed all day, which we don't recommend! You might be able to address your high morning blood pressure by changing when you take your medications. The effects of some blood pressure drugs remain pretty constant over time, even during sleep. But others are broken down quickly, and their effect may wane overnight, leading to high morning readings.

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