If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Intro to hypertension (systolic and diastolic blood pressure)

Learn the categories of hypertension for systolic and diastolic blood pressures. Rishi is a pediatric infectious disease physician and works at Khan Academy. Created by Rishi Desai.

Want to join the conversation?

Video transcript

Let's talk about hypertension. And I'll write that here, hypertension. And hypertension basically means high blood pressure. And we actually categorize it in different groups. So let's use my blood pressure, 115 over 75 as an example. And I had drawn a small figure for you where I had blood pressure on this side and I had time on this side. And I said at my blood pressure does something like that, where the peak is 115. This is the systolic blood pressure. And I said that the lowest point is going to be, for me, 75. And that was my diastolic blood pressure. And we know everyone has a different blood pressure. So let's organize blood pressures into groups. Let's say, let's figure out what group goes where. And so, to do that, I'm going to draw a couple number lines. So let's imagine that I have, here in brown, I'll do my systolic blood pressure on this side. And I'll do the diastolic on the other side. I'll do diastolic over here. And we're going to actually put them next to each other. And I'll try to make about the same size, like that. So let's say this is really high pressure. This would be like 200. And this is all in millimeters of mercury. 200 millimeters of mercury. And at the very bottom would be 0. So let's make them kind of the same. And that means that up here would be about 100. And this would be about-- let's say this is 120. This would be about 140, let's say. Maybe this is 160. And this is 180. And I'm going to do the same thing here. Let's say this is about 100, except this time I'm going to go the other side. Let's say this is about 80, and this is 60, 40, 20. Maybe I didn't draw it as well, but I think you get the idea. So this is my number line. And the reason I drew the systolic numbers higher than the diastolics is because we know that generally speaking-- or not generally speaking-- always the systolic pressure is going to be higher than the diastolic pressure. So that's why I separated it out. But you can imagine that these numbers go up and these go down. I'm just being lazy not drawing it all out. So let's say that my pressure is 115. This in my systolic pressure. Now let's do that one first. Where does that fit? Well, on this number line, 115 would be about right here. And actually anything below 120 is actually kind of in the green zone. And this goes all the way down, to 0. So let's say my systolic was 97, or 103. That would all be in the green zone. And what I mean by that is, I would say I do not have hypertension. I have no hypertension. So that's kind of a nice, safe, area to have your blood pressure in, in terms of hypertension. Now for diastolic pressures, we know that diastolic pressures are the low range of a blood pressure. And so those numbers are going to be lower. Here, anything below 80 is considered in that safe green zone. So below 80 is where you want to be. And I want to be very specific, I don't mean to say that a blood pressure of 5 would be good. What I mean is that you don't have hypertension. So you don't have high blood pressure. And that's where it's different from having low blood pressure. So just for right now, the green zone in terms of high blood pressure. Now, let's say my systolic blood pressure was a little bit higher. Let's say it's between 120 and 140, somewhere in here. Then I'm in the yellow zone. And that yellow zone means that I don't have hypertension, but I'm getting there. So I'm getting closer, and this would be prehypertension. And on the other side, on the diastolic side, we use 90 as a cut off. So I'll write in 90. And anything between 80 and 90 would be kind of in that yellow zone. And that's your prehypertension zone. It's prehypertension. So you're still not there yet. Now in terms of high blood pressures-- again, you don't want high blood pressures-- but in terms of getting there, if you're above 140, you have hypertension. So this zone in here, 140 to 160 in particular, is considered stage one hypertension. And between 90 and 100 for diastolics, that would be stage one. And now if you have something above 160 for your systolic blood pressure-- so I'll just say above 160, and that means even higher than 200, so if let's say you have 201-- that would be stage two. So you can see that the higher you go, the higher your stage number. And the same is true on this side. So let's say you have a really high diastolic blood pressure, well above 100. You'd have stage two hypertension. All the way down there, this is stage two. So I'm just going to do a couple quick examples for you. So let's say-- I'll do them in yellow, different color-- let's say that you have 145 as a systolic. And your diastolic is, let's say, 87. Well, 145 is right here, right? And 87-- actually, let me do it the same color just to be consistent. So 145 is right here. And 87 is in here. So your systolic pressure is stage one hypertension, and your diastolic pressure is in prehypertension. So when you're in different stages for the diastolic and the systolic what you do, the rule, is that you go with the higher stage. So in this case, stage one is higher. So this person would be considered stage one hypertension. Now we can do one more example, just to make sure you get it. So let's do a different color. Let's say I'll do the next one in red. So you have, let's say 126 over, let's say 101. Well, this person, 126 is actually right here. And 101 is right above the 100 mark, right there. So this person is actually prehypertensive if you're looking at just their systolic value. But they're actually in stage two hypertension if you're looking at the diastolic value. So overall, they're going to be in stage two, because the rule, again, is that you go with the higher stage. So that's how you figure out what stage of hypertension someone's in.