Dear Dr. Roach: I read on the internet that you should take your blood pressure medicine at night. I just recently started taking medicine for my blood pressure and my instructions were to take it first thing in the morning. So, when is the best time to take it?
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A: A study published last October showed that, as a group, people who were told to take all their high blood pressure medicines at night had surprisingly fewer bad events (heart attack, heart failure, stroke, procedure to open heart blood vessels or death due to cardiovascular causes) than people who were told to take their medicines in the morning. Subjects in the study could be taking any of the major types of blood pressure medicines that are normally given once daily.
The reason those who took their medicines at night did so much better may be related to normal physiology. During sleep, the blood pressure normally dips down. In some people, there is a diminished "dip" or even the opposite occurs -- a rise in blood pressure. Taking blood pressure medicine at nighttime restored or enhanced the normal response. In addition, blood pressure normally rises around 6:00 in the morning, timed with an increase in the blood levels of the hormone cortisol. This is the peak time for heart attacks. It's possible that having protection from high blood pressure at this time from taking it at night could help prevent heart attacks. That's opposed to those taking it during the day; at 6 a.m., the medicine is wearing off and protection is at its lowest.
The findings in the study are dramatic. There was a 45% relative risk reduction in the number of people who had any of the bad outcomes studied. This translates to about 1 person in 18 over the six years of the study not getting an event, or an absolute risk reduction of just over 5%.
Some of my colleagues have already started telling their patients to change the time they take their blood pressure medicines to nighttime. I would caution against doing so without talking to your doctor. I would also add that taking diuretics at bedtime can cause some people to have to get up during the night.