Which Number on Your Blood Pressure Reading Is More Important?

When it comes to your health, knowledge is power — and that’s why it’s vital to know your blood pressure levels. Chances are good that your doctor has taken your blood pressure at your annual appointment and relayed how healthy or unhealthy your levels are. But even if you know the top number and the bottom number, do you know the difference in what they’re measuring? And if one number is an unhealthy range while the other is normal, do you know if it’s still cause for concern?

Here’s the truth about which number on your blood pressure reading you should be paying attention to more.

The top number vs. the bottom number: What do they mean?

Nurse checking a patient's blood pressure

Nurse checking a patient’s blood pressure | Zinkevych/iStock/Getty Images

Before delving into which number is the one you should be more concerned with, it’s vital to know what the two numbers on your reading indicate. The top number, which is always higher than the bottom, is known as your systolic blood pressure. It’s the measure of the pressure of your blood against your blood vessels when your heart is pumping. There are certain normal, everyday situations that cause your systolic pressure to rise temporarily, too. Exercising and stress, for example, can cause this to occur.

The bottom number — and lower number of the two — is known as your diastolic blood pressure. While the top number measures your blood pressure when your heart is beating, the diastolic number is the measure of your blood pressure when your heart is between beats.

As for what blood pressure you should be shooting for, slightly below 120/80 is best. If your systolic number is above 120 or your diastolic number is above 80, this could signal you’re on your way to high blood pressure.

It was always thought that the bottom number was more important

As for which number is more important, the medical community hasn’t always agreed. WebMD explains many medical professionals put their focus more on the diastolic reading for years. As Donald Lloyd-Jones, M.D., told the publication, “There has been this historical bias assuming that diastolic blood pressure and diastolic hypertension were more important and more risky than systolic hypertension.”

So, why did they put their focus on the lower number? Lloyd-Jones explains doctors thought of the lower number as the “baseline pressure,” whereas the top number was just the brief moment the heart pumped blood. For this reason, doctors disregarded the top number and only aggressively started treating high blood pressure if the bottom number was too high. It was also thought to be somewhat normal to see the top number climb with age, but that can actually be an indicator of ill health.

Now, doctors are paying more attention to the top number

elements of blood pressure

Stethoscope and blood pressure monitor | iStock.com

Nowadays, doctors know that both numbers need to be looked at to determine the health of a patient. And Blood Pressure UK even suggests that the top number is more important than the bottom. The publication notes, “Having a raised systolic blood pressure but normal or low diastolic blood pressure is called Isolated Systolic Hypertension (ISH) and carries an increased risk of developing heart attacks or strokes and should be treated.”

Lloyd-Jones also mentions that your blood pressure stage is determined by both numbers — but “far more often the systolic pressure determined what stage you should be in. … We are trying to raise awareness in clinicians, policy makers, and patients that we really need to be paying attention to the systolic elevation.”

Above all else, you’re better off knowing and understanding both of your blood pressure numbers. But if one number is higher — whether it’s the top or the bottom — ask your doctor about what you can be doing to lower them. High blood pressure can lead to heart disease or stroke, so taking it seriously can be life-saving.

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