by Ken Westover

This page is for information purposes only!
Always consult your doctor for the latest and best information!

 - What is Hypertension?
 - Do You Have Hypertension?
 - What is Blood Pressure (BP)?
 - Measuring Blood Pressure
 - Devices for measuring BP
 - Blood Pressure Ranges (table)
 - Why Hypertension is Bad
 - Dietary Influences
     DASH Diet
     DASH-2 (DASH-Salt)
 - Physical Influences
 - Drugs for BP control
 - Glossary
 - Sources
rev: 2012Aug09

What is Blood Pressure?

Your heart pumps blood in a way similar to squeezing the middle of a long balloon. When your heart contracts blood is forced out of the heart and into the vessels. This sudden surge of pressure is called the systolic (sis-TALL-ik) pressure.

When the heart relaxes blood is sucked into the heart from the veins, like air filling the balloon when you relax your hand. A series of valves makes the blood flow in one direction, so blood won't flow backwards into the heart from the arteries (like air does in the balloon example). When your heart relaxes, the pressure drops to a low point called the the diastolic (die-a-STALL-ik) pressure.

These two pressures specify your blood pressure, which is expressed as systolic "over" diastolic, like "120 over 80".

What is Hypertension?

Hypertension means high blood pressure. ("hyper" = beyond normal, excessive. "tension" = pressure)

Why Hypertension is Bad

Hypertension makes you more likely to have a heart attack or stroke. That is, it's a "risk factor" for two of the top killers in America. Like water in a hose, blood puts pressure on the vessels. Excessive pressure can cause various things to fail, like blood vessels, kidneys, and other organs.

Hypertension doesn't have direct symptoms. You only know you have it if you measure your blood pressure.

Causes of Hypertension

In about 95% of people with high blood pressure, the cause isn't known. {Wikipedia} This type of hypertension is called "essential", "primary", or "idiopathic" hypertension. If the cause is known, it is called "secondary" hypertension.

Identifiable causes of hypertension
Sleep apnea
Drug-induced or related causes (see table 9)
Chronic kidney disease
Primary aldosteronism
Renovascular disease
Chronic steroid therapy and Cushing's syndrome
Coarctation of the aorta
Thyroid or parathyroid disease
(from JNC7 Express p6, table 3)

Do You Have Hypertension?

In 2003 the NIH established new ranges and classifications. Look up your readings to see what the table recommends.

Blood Pressure Ranges
...... Systolic   Diastolic Classification Action
or up
Hypertension, Stage 2 Medical evaluation 
2-drug combination
or 99
Hypertension, Stage 1 Medical evaluation 
 Take diuretic (Thiazide-type)
or 89
Pre-hypertension Begin
life-style modifications
and 79
Normal Consider 
life-style modifications 
The higher of systolic and diastolic is used to decide the classification.
Table based on JNC 7.

In May 2003, during official Blood Pressure Month, it was announced that the range from 120/80 to 140/90 was being called "Pre-Hypertensive". A study showed that a change in pressure is more important than previously thought.

The study is formally called: The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7).

An "Express" version of the study has been released before the detailed version. This Express version is 52-pages long and available from http://www.nhlbi.nih.gov/guidelines/hypertension/index.htm.

The table below is provided for those familiar with previous recommendations. This is now considered outdated in light of the latest studies.

If your doctor is quoting you information from this table, he/she is not up with the latest information. Visit the National Institutes of Health web site and print a copy of the 52-page JNC 7 "Express" report for your doctor. (Many doctors are overworked and can't keep up with EVERY new study as soon as it comes out.)

OLD (pre-May 2003) Blood Pressure Ranges
Systolic . Diastolic Classification Action
210+ or 120+ Hypertension, Stage 4 (very severe) Medical evaluation
(still got a pulse?)
or 119
Hypertension, Stage 3 (severe) Medical evaluation
Begin treatment within 1 week
or 109
Hypertension, Stage 2 (moderate) Medical evaluation
Begin treatment within 1 month
or 99
Hypertension, Stage 1 (mild) Confirm in 2 months
Begin life-style modifications
or 89
High, normal Recheck in 1 year
Begin life-style modifications.
If no change, consider therapy.
and 85
Normal Recheck in 2 years
and 80
Optimal Recheck in 2 years

Measuring Blood Pressure

There are several different devices for measuring BP, which I'll get to in a moment, but first,

You Must Relax!

Regardless of the device, it's important that you be relaxed before the reading is taken. You can't leave your car in a "No Parking" zone as you run into the pharmacy to get a quick BP reading off their machine. Some sources say you should sit or lie still for five minutes before taking a reading.

Stress can temporarily raise blood pressure. The stress of just being in a doctor's office can cause "white coat hypertension", where someone with normal BP shows a temporarily high reading.

Since several factors can cause blood pressure to rise temporarily, multiple readings should be taken spread over days. Don't let one high reading give you a heart attack.

Basic Measurement Process

Your blood pressure is expressed as two numbers, a high number "over" a low number. Both numbers are pressures. Your pulse is often taken at the same time, so you may have a third number somewhere. Your pulse is simply how many times your heart beats per minute.

BP is measured by listening to blood flow through an artery. A cuff is placed around an artery and is inflated while listening to the blood. The cuff is inflated until you hear the blood stop flowing.

Systolic (high number): The cuff is now slowly relaxed until you hear blood just start to flow. That's the high (systolic) number.

Diastolic (low number): At the systolic pressure the blood flow sounds "funny" because the artery is still mostly squished. The cuff is relaxed further until the blood flow sounds normal. That's the low (diastolic) number.

A human can listen to blood flow using a stethoscope. A machine uses a small microphone in the cuff.

Which arm/arms?

You want to measure BP as close to the heart as practical, which is typically the left arm (what the patient calls "left"). To be thorough, BP should be measured on both left and right arms - the BPs should be close. If they are very different, it could indicate an artery is blocked on one side.

Sitting or Standing?

BP is normally taken while sitting. BP may then be taken while standing to see how well the system responds to change.

When you stand up, gravity pulls blood away from the brain, which makes the brain unhappy and can make you feel dizzy. If there's too little blood (oxygen), the brain makes you faint ("syncope")  so your head/brain will soon be at ground level, where the blood can flow back into the brain (and start repairs on any damage from the fall).

The body responds in many ways to get the blood pressure back up to where it can move blood through the brain. Nerve impulses tell the blood vessels to constrict, and to make the heart beat differently. In the elderly, nerve impulses travel more slowly, so they need more time to adjust after standing before they can move safely.

Devices for Measuring Blood Pressure


These are the most accurate, and are what you usually see in a doctor's office. A column of mercury rises and falls in a tube just like a thermometer (which originally was mercury also). Due to concern about mercury spills if something breaks, we are seeing fewer devices using mercury. But it's still the most accurate measurement.

Machines in Stores

You can use one of those machines in the pharmacy section of some stores to get an idea of your blood pressure. Though not "doctor's office accurate", they can alert you to pressures you should ask your doctor about. If possible, try to relax a bit before taking the reading (since you were probably rushing around before stopping at the machine).

Home Monitors

Home monitors are rated in Consumer Reports October, 2011, p. 38-39. Of 21 models tested, 14 were recommended. Two models are compatible with iPhone, iPad, and iPodTouch when used with a free downloadable app.

Only two types were evaluated: arm and wrist.

Arm Monitors

The cuff is automatically inflated and deflated, and the readings appear in a digital display. These run on batteries or an AC adapter that plugs in the wall. Prices range from $46-$110.

Wrist Monitors

The cuff goes around your wrist instead of your arm. These tend to be less accurate perhaps because arm position has an effect. Prices for recommended models range from $50-$60.

Manual (Semi-automatic) Arm Monitors

The cuff is controlled by a bulb you squeeze yourself while the machine listens and displays the readings. Previously said to be the hardest to use, these were not tested in the 2011 or 2012 reports.

Fingertip Monitors

These were not tested in the 2011 or 2012 reports.

Dietary Approaches to Stop Hypertension (DASH)

Two studies were done to see if blood pressure (BP) could be lowered by diet alone.

The first DASH study ignored sodium (salt). The resulting "DASH" diet lowered blood pressure by 5.5 points (systolic) over 3.0 points (diastolic) in eight weeks.

The second DASH study took the diet from the first study and looked only at the effect salt had on BP. The resulting DASH-2 diet (limiting sale intake) lowered blood pressure by 8.9 points over 4.5 points.

The latest DASH diet recommendations came out in May, 2003, and be found at the National Institutes of Health web site: The DASH Eating Plan (Updated May 2003)

DASH Study Details

In 1997 a study was conducted to learn more about an odd observation: People who ate food rich in potassium, calcium, magnesium, protein and fiber had low blood pressure. When given supplements of those nutrients, only potassium had any effect. It appeared something in the food had an effect beyond the isolated nutrients (trace nutrients?). That is, taking supplements was less effective than eating the right foods.

But what were the right foods? The DASH study used the following diet:

Original DASH Diet (2,000 calories each day)
Food Servings Each 1 Serving is
Grains & grain products 7-8 day 1 slice bread
1/2 cup dry cereal
1/2 cup cooked rice, pasta or cereal
Vegetables 4-5 day 1 cup raw leafy
1/2 cup raw non-leafy
1/2 cup cooked
3/4 cup juice
Fruits 4-5 day 3/4 cup juice
1 medium
1/2 cup fresh, frozen, or canned
1/4 cup dried
Dairy, low- or non-fat 2-3 day 1 cup milk, 1% or fat-free
1 cup yogurt, low-fat
1.5 ounce cheese, non-fat
Meat (lean)
Poultry (skinless)
2 or less day 3 ounce broiled or roasted
4-5 week 1/3 cup nuts
2 Tbs. sunflower seeds
1/2 cup cooked beans
Added Fat, oil, salad dressing 2-3 day 1 tsp. oil or soft margarine
1 tsp. mayonnaise, regular
1 Tbs. mayonnaise, low-fat
1 Tbs. salad dressing, regular
1 Tbs. salad dressing, light
Snacks & sweets 5 week 1 medium fruit
1 cup yogurt, low-fat
1/2 cup frozen yogurt, low-fat
3/4 cup pretzels
1 Tbs. maple syrup, sugar, jelly, jam
1/2 cup Jell-O
3 pieces hard candy
15 jelly beans

DASH article: Nutrition Action Health Letter October 1997 (http://www.cspinet.org/nah/dash.htm)
This article explains the study in everyday terms.

DASH-2 (DASH-Salt)

To evaluate sodium, a second study was done by modifying the original DASH diet to limit sodium. Three levels of daily sodium consumption were tested: 3300 mg, 2400 mg, and 1500 mg.

Blood pressure fell with decreased sodium intake. The lowest sodium group (1,500 mg) lowered their blood pressure by 8.9 points (systolic) over 4.5 points (diastolic).

Put another way, subjects with Stage 1 hypertension dropped blood pressure as much or more than any anti-hypertensive drug had done.

To make your own DASH-2 Diet, take the Original DASH Diet and limit sodium to 1,500 mg per day. This can be helped greatly by limiting intake of processed food. Read the labels to see Sodium contents.

Dietary Influences


Sodium is required for good health. It is commonly (over-)eaten as table salt, which is sodium chloride (chemical symbol NaCl). Humans like the taste of salt and tend to eat a lot of it. It is routinely added to processed foods, to which more may be added in the kitchen and at the dining table.

The contribution of sodium to hypertension has apparently been settled with the DASH-2 study: Sodium can increase hypertension. However you feel about that study, UC Berkeley wisely observed: "A high-sodium diet has no advantages and many disadvantages."

(Author's Aside: If you automatically salt your food before tasting it, stop it! Not only does it piss off the chef who so carefully seasoned it already, it shows you aren't thinking, but running on habit - an unhealthy habit at that.)


Caffeine can raise blood pressure, but this appears to be a temporary rise. Caffeine is not known to cause hypertension. {UCB}

Physical Influences


Excess weight will increase blood pressure. To check if you are really overweight or not, visit "Aim for a Healthy Weight" (http://www.health.gov/dietaryguidelines/dga2000/document/aim.htm#weight_top)

Eliminating excess weight is perhaps the healthiest way to reduce blood pressure.


As people get older, the arteries tend to be less flexible (from build-up of plaque). The reduced flexibility can increase blood pressure. (So stop eating foods that add plaque to your arteries!)

Also, as we age, nerve impulses travel more slowly. Messages between the brain and circulatory system make BP less responsive to change.


Of course smoking increases blood pressure. Even one cigarette can raise your blood pressure. There is NOthing physically beneficial about smoking. In your heart, literally, you know it's bad. Stop it.

Drugs Used for BP

This section is to show what class of drugs your prescription falls into. This may stimulate a discussion with your doctor about what type of medication you should be taking. For example, a recent (2002-3) study showed diuretics were still very effective, even when compared to newer types of drugs.

Blood Pressure Drugs
Class Generic Name Brand name
Diuretics Chlorthalidone
HydroDiuril, Microzide
Beta-blockers Atenolol
Lopressor, Toprol-XL
Inderal LA
ACE inhibitors Enalapril
Prinivil, Zestril
Calcium channel blockers Amlodipine
Cardizem CD, Dilacor-XR
Adalat CC, Procardia XL
table based on Consumer Reports May, 1999 p61

Detailed Theory

Measuring Blood Pressure

Medical folks use a blood pressure cuff (sphygmomanometer: sphygmo = the pulse, manometer = pressure measuring instrument) and stethoscope. The cuff is wrapped around an artery about the level of the heart, usually in your arm. The stethoscope is positioned over that artery, "downstream" from the cuff, to hear blood flow during the following process.

The cuff is inflated until the artery is squeezed closed (hear the blood stop flowing). The cuff is slowly deflated while listening for blood flow to resume. When you first hear flow start, that's the systolic pressure.

Although blood is flowing, it sounds turbulent (noisy). Cuff pressure is slowly reduced until the flow sounds smooth. This is the diastolic pressure.

The units of measurements are millimeters (abbreviated "mm") of mercury (symbol "Hg").


A vessel carrying blood AWAY FROM the heart
A blood vessel about 0.1 mm diameter, smaller than an artery, larger than a capillary. Arterioles have muscle fibers in their walls (!) that can contract when stimulated. Contraction can be stimulated electrically (nerve impulses) or chemically (hormones). This is one mechanism the body uses to adjust blood pressure.
A tiny blood vessel connecting artery to vein. It is slightly larger than a single blood cell. Capillaries are everywhere so most cells are near one.
A vessel of intermediate size, larger than a capillary, smaller than a vein. capillaries merge into venules on their way to veins.
A vessel carrying blood TOWARDS the heart
A tube or duct for circulating a fluid, like blood. This term includes arteries, veins, and all their connections.



The latest information about blood pressure from the government comes from the National Institutes of Health, specifically, the Heart, Lung, and Blood Institute. They conduct the studies and report the results to the world, including your doctor and the press. Their web site has information for all levels of understanding, from doctor to common folk. It has a summary of the latest blood pressure studies and latest DASH diet recommendations. Visit: http://www.nhlbi.nih.gov/guidelines/hypertension/index.htm.

Anderson and Young. Diet and Hypertension. no. 9.318 March, 2002.
DASH article: Nutrition Action Health Letter October 1997
National Heart, Lung, and Blood Institute

Facts About the DASH Diet


The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7 Express). NIH Publication No. 03-5233. May 2003.

Blood Pressure Monitors. Consumer Reports June 2003. p. 22-24.
Blood Pressure Monitors. Consumer Reports October 2011. p. 38-39.
Blood pressure monitors go mobile. Consumer Reports June 2012. p. 41.
High Blood Pressure: The End of an Epidemic?. Nutrition Action Health Letter December 2000 p.3-9
Hypertension: What Works? Consumer Reports p. 60 May, 1999.
Davidovits, Paul. 1975. Physics in Biology and Medicine.