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MIAMI (CBSMiami) – For the first time in more than a decade, the guidelines for high blood pressure are changing.

The American Heart Association and American College of Cardiology are defining a top reading of 130 or more or a bottom reading of 80 or more as high blood pressure.

This means nearly half the U.S. adult population is living with hypertension and at an increased risk for heart disease and stroke.

The old definition of high was 140 over 90.

Charles Cronenweth has been working to lower his blood pressure for the last 10 years.

Tens of millions more Americans will soon be learning they have hypertension.

“Most of them just need to know they are at high risk, but they can manage that problem on their own,” said Dr. Paul Whelton, leading author on AHA/ACA Guidelines.

The change is expected to have the biggest impact on men and who are under the age of 45.

“They would have to exercise more, have a better diet – a diet that is low in sodium, restrict alcohol and lower stress,” Dr. Ravi Dave, Professor of Medicine at UCLA Health.

Under the new guidelines, 120 or less is still normal blood pressure but up to 129 is considered elevated.

And at 130 begin different stages of high blood pressure and an increasing risk of heart attack and stroke.

Even though 14 percent more people will be diagnosed with high blood pressure, only a small portion will take home prescriptions.

“Preventing hypertension is much better than getting hypertension,” said Dr. Whelton. “It’s good to treat it when it’s there, but it is way better to prevent it.”

Cronenweth says he checks his blood pressure every day and more Americans will be getting instructions on how to do that.

“I try to eat a heart healthy diet and exercise 3 or 4 times a week,” added Cronenweth.

The new guidelines emphasize making sure blood pressure readings are accurate.

The authors says blood pressure levels should be based on two or three readings at least two different times and that people should learn the proper techniques for checking their blood pressure at home.