Blood pressure varies, so when is it hypertension?

My blood pressure averages 128/78 in the morning. Basically normal.

But after getting home from a day at work and a half-hour of traffic (man, I hate traffic) it jumps to an average of 145/80. That’s high.

A little later in the evening it averages 130/80. That’s borderline high.

So: Do I have high blood pressure? Borderline? Or normal?

While we’re on the topic, do caffeine and salt have acute or chronic effects on BP?

Good questions – let’s ask about acute and/or chronic effects on BP from alcohol as well…


Hypertension has traditionally been defined as anything above 140/90 (sustained). It may be the case that persistent readings above 130/85 is a better definition.

If a person has diseases which by themselves increase the risk of stroke, heart attack, or kidney damage (eg. diabeted), most people would use the lower range for defining normal, or at least desirable.

Alcohol has a potent effect to raise blood pressure.It should be avoided or minimized in anyone with hypertension.

Although I stand to be corrected, my belief is that there is a role of dietary salt restriction in the treatment of hypertension. See for example this consensus recommendation. Others would disagree

Some other links:
American Heart Ass’n

Let’s see what Qadgop says.

What about body size? It seems to me that someone who is 6’5" tall would need more blood pressure just to distribute the blood the extra foot over someone who is 5’5", even if they were the same body shape.

Is that so, or would it make no difference or only a slight difference?

If the 6’5" man’s pressure is strong enough to get the blood to all his body and still maintain a steady 140/90 then he has high blood pressure. If his blood pressure is 120/80 then obviously his heart is pumping stronger than a 5’1" 100 lb. woman’s heart is pumping to keep her pressure at 120/80, but they are both in good health.

The last figure xx/80 is the more important of the two. A doctor will usually but you on medication for 90 or above.

Let’s put it another way. If you laid a 100 foot pipeline to your swimming pool and they told you that it could withstand 250 lbs of pressure, could you make the pipe 200 foot long and make it withstand 400 lbs of pressure?

How is the “normal” range of any medical measurement established? The usual starting point is to measure lots of people to get a bell curve, then decide arbitrarily on a cut-off. Usually this is the lowest and highest 2.5% or 5%, sometimes other values are used (e.g. in pediatric development just the lowest 25% and 10%).

High blood pressure guidelines are put out by Consensus Committees working with national Heart & Stroke Associations. Several studies have shown a strong benefit to reducing blood pressure below 140/90, lower in diabetics, pregnant women and some other people.

But these aren’t etched in stone and as KarlGauss says will likely come down further. The top number, when the heart is pumping (systolic pressure) is now thought to be less important than the diastolic pressure (lower number) when the heart is relaxed and refilling with blood.

In reality, both are important. Your doctor would not be concerned by one high blood pressure measurement in the absence of symptoms like headache. Ideally, you would not be started on blood pressure medications unless it was persistently elevated over months… though this can be a problem in some people who just have high blood pressure due to the anxiety of getting it measured but are otherwise “normal”.

Everybody’s blood pressure changes throughout the day. A more accurate measurement of hypertension might incorporate the mean arterial pressure (which incorporates both numbers) or changes in blood pressure over time for that person.

The length of the tube is not proportional to the pressure it can handle. Tall people cannot withstand much higher pressures to my knowledge. Arteries are very elastic and very different from rigid pipes which offer quite a limited analogy. In general, the problems from high blood pressure are not just arterial rupture (some strokes) but also eye damage, kidney damage, heart damage and headaches.

The importance of salt is controversial. Where there is salt, there is water, so physiologically salt restriction makes sense. In practice though, most people with working kidneys seem to be able to compensate for this. I believe it depends on the person and recommend salt restriction only in some people, since unsalted diets taste gross.

Caffeine and alcohol likely raise blood pressure.

Dr_Pap, B.Eng, M.D.

Body size is measured in a parameter called the cariac index. Without getting too detailed:

Cardiac output = Stroke volume * Heart rate

Cardiac index = Cardiac output / Body Surface Area

Usually no cause can be found for high blood pressure. Some causes, however, include hyperaldosteronism, NSAID (aspirin or Advil) use, kidney artery narrowing, Conn’s syndrome, endocrine tumours or problems with the aorta.

KarlGauss and Doc Pap just let me add this qualifier to your answers: