The Family Health Guide

Prehypertension: Does it really matter?

As doctors took blood pressure readings on millions of people over the years, it became clear that hypertension is a major threat to health, increasing the risk of stroke, heart attack, congestive heart failure, kidney failure, and visual loss. And as data accumulated, it also became clear that there is no bright line between a healthy blood pressure and a harmful one; in general, the lower the pressure, the better.

Nevertheless, doctors need a target for blood pressure, and patients also need a goal. Those goals changed in 2003, bringing the threshold for a normal blood pressure reading lower than ever before, at 120/80 millimeters of mercury (mm Hg), and it also established a new diagnostic category of "prehypertension" (see table).

Classification of blood pressure for people 18 years or older


Systolic BP

Diastolic BP


below 120

below 80




Stage 1 hypertension



Stage 2 hypertension



Systolic blood pressure (BP) is the number recorded when the heart is pumping blood into the arteries; diastolic BP is the number recorded while the heart is refilling with blood between beats. All units are in mm Hg.

Which number?

The revised standards provide simple guidelines for interpreting blood pressure readings, but each reading generates two numbers. What if your systolic and diastolic readings contradict each other? To determine your classification, use the number that puts you in the higher group. For example, if your reading is 114/84, you have prehypertension.

Each person has two arms; pressure readings often differ between them, sometimes by 10 mm Hg or more. Which arm should you use to determine your classification? It's not a question of right vs. left but of right vs. wrong: Use the arm with the higher reading.

Blood pressure readings can vary from time to time. Should you worry about your peaks or take comfort from your valleys? Classification depends on your usual or average blood pressure rather than occasional extremes. For most people, a careful reading during an annual checkup will suffice. But people with prehypertension or hypertension should have their readings checked more often to get a true picture.

A new diagnosis

Prehypertension is not an illness — but it is an important warning that illness lies ahead. Prehypertension increases the risk of developing hypertension, a major illness indeed.

Prehypertension increases the risk of heart disease. According to a 2005 analysis by the Framingham Heart Study, men with prehypertension are 3.5 times more likely to suffer heart attacks than those with normal blood pressures. Surprisingly, although high blood pressure is a major cause of strokes, prehypertension did not appear to increase the risk of stroke.

What to do?

First, know your blood pressure. That means having it measured by a health care professional or measuring it yourself with a high-quality home blood pressure machine. Don't count on headaches, nosebleeds, a red face, or mental stress to warn you that your pressure is too high — none of these traditional signs is reliable. Instead, have your pressure measured with every check-up; once a year is ideal.

Second, find out if you have other cardiovascular risk factors such as abnormal cholesterol levels, diabetes, a sedentary lifestyle, obesity, tobacco abuse, and mental stress.


For most prehypertensives, treatment should depend on lifestyle changes, not medications. Here's what to do:

Diet. The Dietary Approaches to Stop Hypertension, or DASH, program is best. It involves a reduction in dietary sodium to 2,300 mg a day or less; 1,500 mg a day is the tough new goal for people with hypertension and for everyone who is middle-aged or older. The DASH diet also calls for a low consumption of animal fat and processed foods.

Exercise. As little as 30 minutes of moderate exercise, such as brisk walking, will produce enormous benefits — as long as you do it nearly every day.

Weight control. One of the most important ways to reduce blood pressure, it's also one of the hardest to achieve. A calorie-restricted healthful diet, such as DASH, plus regular exercise can help.

Moderate alcohol use. Small amounts of alcohol won't raise your pressure, but heavier drinking will. If you choose to drink, limit yourself to two drinks per day, counting 5 ounces of wine, 12 ounces of beer, or 1½ ounces of spirits as one drink. Low-dose alcohol appears to reduce the risk of heart disease and stroke, but no one should take up drinking strictly for its medical benefits.

Stress control. It's harder to quantify than the other lifestyle goals, but a number of studies suggest that meditation and other relaxation techniques can help lower blood pressure. Healthful living will prevent many cases of high blood pressure, and it can replace or reduce medications for many hypertensives.

Medication. Should you take medication for prehypertension? It's an important question, but doctors don't know the answer. They do know that readings below 120/80 are best, but they don't know if medication should be used to reach that low goal. More study is needed. But even now, patients with diabetes, chronic kidney disease, and heart disease should take medicine if that's what's needed to bring their pressures below 130/80.

April 2007 update

Diastolic BP

below 80