Research shows four million Australians are at risk of heart attack because of high or untreated blood pressure, and city dwellers are the worse culprits.

Millions of Australians are walking around like "ticking time-bombs", unaware they're at risk of a stroke or heart attack because of their dangerously high blood pressure.

Heart Foundation analysis of the latest data from the Australian Bureau of Statistics, released on Sunday, shows a quarter of Australian adults have high blood pressure that is either untreated or treated inadequately.

This equates to four million people at risk of a heart attack or stroke.

High blood pressure is the biggest risk factor for many of the biggest killers and Heart Foundation national CEO, Adjunct Professor John Kelly says too many Australians are putting their lives at risk by not keeping it in check.

"In Australia, more deaths can be put down to high blood pressure than to any other single risk factor," said Prof Kelly.

Hypertension also causes other serious illnesses like dementia and kidney disease, says Prof Kelly, and people should be aiming to have their blood pressure checked at least every two years.

"If you don't know whether your blood pressure is OK you need to see your doctor," urged Prof Kelly.

The Heart Foundation analysis discovered those already taking medication, one in four - or 1.4 million - still have "dangerously" high blood pressure.

City people are the worst culprits for not keeping the high blood pressure in check, according to the data.

While people in the country are more likely to have hypertension, 39 per cent compared to 31 per cent, they are more like to have it properly treated.

"We think that's probably because there is a closer relationship between country people and their local GP or doctor," said Prof Kelly.

Alarmingly, just seven per cent of people are aware that high blood pressure is the largest risk factor for heart disease.

The good news is that eating a healthy diet, quitting smoking and being physically active can all help to reduce blood pressure.

Reducing stress is also vitally important.

"If you just exercise more and eat healthy food you have a better chance or reducing your risk of hypertension," said Prof Kelly.

"Heart attacks and cardiovascular incidents kill more Australians than any type of disease, for men and women it's the biggest killer in Australia."

KEY STATISTICS:

• Number of Australians with hypertension - 5984.2 (33.7 per cent)
• Metro residents with hypertension - 3256.3 (30.5 per cent)
• Regional/rural residents with hypertension - 2727.9 (38.6 per cent)
• Percentage of metro residents with unmanaged hypertension - 51.7
• Percentage of regional/rural residents with unmanaged hypertension - 36.5.