What do the blood pressure numbers mean and how do they relate to each other?



Basically, I’ve always been really healthy, went to the doctor, got my BP (104/68) and was told it’s really healthy.

Then I said (to my Mom, an RN) “would it be better to be 104/80 or 104/60” and she just looked at me like I was crazy, then told me 104/60. Then I said, “but would it be better to be 100/72 or 104/68?” And she was just done with me at that point and I just don’t understand what these numbers mean and the internet is too advanced for me.

In: Biology

Top number is how much push when heart is beating. Bottom number is how much pressure between heartbeats. 80 on the bottom counts as “elevated” so it’s just barely too much but not quite considered “high”
Too low is not great (mine is usually in the 50s), but it’s less harmful than too high.

The top number is referred to as the systolic blood pressure, and the number is a measure of the pressure of blood against the walls of your arteries as your ventricles (lower two chambers of the heart) push blood throughout the body.

The bottom number is referred to as the diastolic blood pressure, and the number is a measure of the pressure of blood against the walls of your arteries as your heart relaxes and the ventricles fill with blood. This is also the period where the heart relaxes in between heart beats.

Generally speaking, a systolic pressure higher than 120 is a problem, whereas a diastolic pressure higher than 80 is a problem. So there isn’t really an issue if you are below those values except if they get too low (such as 90/60 or below).

If you think about it, the only normal way to get super low diastolic (bottom number, pressure of “sitting around” blood that isn’t actively being pumped) is to be low on blood volume – major dehydration, blood loss – or to have an active leak (so blood loss again except that it’s still coming out).

IANAD but maybe there are also weird syndromes that give you loose or stretchy blood vessels?

ELI5: top number is when the heart is squeezing. The bottom number is when the heart is relaxing.

ELI 15: top number is heart squeezing blood out of the heart. Your arteries resist this (because equal/opposite reaction). Bottom number is heart relaxing… your arteries still push back.

As for health of the numbers, that’s a little more than ELI5… but the basics are you want all of the numbers to be lower, including your pulse rate. A heart that only has to beat 60x per minute to perfuse the body is healthier than a heart that has to beat 100x per minute. The normal range of heart rate for an adult is 60-100, with 60 being on the much healthier side. For blood pressure, it’s the same thing. You want the lowest blood pressure you can have. With that, you need something called an “mean arterial pressure”, because you heart pumps blood to all your organs. One of those organs is your kidney, and that needs a mean arterial pressure of 70, otherwise there isn’t enough pressure to filter your blood properly. A BP of 90/50 would be adequate (depending on the person), but a BP of 90/60 would be more safe(as we want the MAP to stay above 70 at all times, and 50 has the potential for your map to be lower than 70)…. 120/80 is considered average. 90-139/50-89 is considered “healthy”. Below those numbers and your kidneys and brain don’t function (or won’t for long). Above those numbers you start looking at stroke range. Then you get into complicated things like a widened or narrowed BP. 100/90, for instance, is a very dangerous BP, as is 180/60 (but for different reasons).

I’m sure you’ve seen one of those blood pressure bags they wrap around your arm to see what you got and then squeeze the bladder to pump into the bag. Think of your heart exactly like hand squeezing the bladder. You gotta squeeze hard to pump air in but relax when filling the bladder to pump more air.

To put it simply, the higher number or the systolic pressure is the pressure exerted on your arteries when your heart squeezes. This number is usually higher because of the work needed to supply your entire body with blood against gravity and your arteries. You can feel this pressure with the old finger-to-neck trick. The lower number or diastolic pressure is the pressure measured of your arteries when your heart relaxes.

To further add to this, your heart is a muscle, and like any other muscle, overworking the heart can have serious complications especially when it is overworking “at rest” (meaning you’re not exerting yourself). So the lower the number, the better it is for your heart (and you).

Why these numbers are different between people is because of the fact that was said earlier: the pressure the pumped blood exerts on the arteries. Those who don’t exercise or eat healthy have narrower arteries due to lack of stimulation and/or fat buildup (called plaque) while those who do exercise work the heart at a higher rate than usual can expand those arterial walls (also why you get an excessive itchy feeling when trying to exercise for the first time in a long while). Triathlons, who are known to push their hearts aggressively and for extended amount of time through exercise, can have super low heart rates such as 80/40 at rest because their heart practically breathes blood through wide open arteries.

The top number is the pressure when the heart squeezes. The bottom number is the pressure when the heart relaxes.

You do need some minimum amount of pressure for blood to flow around the body. Most people have this.

The more common problem is when blood pressure gets too high. It’s not because the heart squeezes harder – it’s because the vessels get clogged and become stiffer, and the heart has to work harder to squeeze against a stiffer vessel. This can happen due to poor diet, smoking, stress, etc. As vessels get clogged and stiffer , they are more likely to leak, rupture, or become too clogged to allow blood through them.

So if the numbers are higher does that mean your arteries are more likely to be clogged? We have a history of high blood pressure and we’re all a little overweight. The doctor just says ooh it’s high, work on it. But they never explain what it means or how to work on it?

This is really much more complex than a simple yes or no on those numbers. The difference of the systolic pressure and the diastolic pressure is called the pulse pressure. 104/80 is a pulse pressure of 24, which is about ideal. 104/60 is a pulse pressure of 44. That’s a bigger “thump” on the artery. Stroke volume also comes into play. Stroke volume X heart rate =Q, the amount of blood pumped. The DBP of 60 would probably indicate less peripheral resistance and atherosclerosis. Pulse should always be considered with the pressures.