People are being urged to take an online heart health test in a bid to reduce dozens of preventable heart-related deaths each day.
The free Heart Age Test is being offered by Public Health England (PHE) as part of a campaign to reduce the number of people who die from a heart attack or a stroke, which stands at 84,100 annually.
A quarter of these deaths are among the under-75s, of which up to 50 a day could have been prevented if those affected had taken action to improve their heart health.
PHE has designed the test to provide those who take it with a "heart age", which can be increased by high cholesterol and high blood pressure.
One in four adults are known to have high blood pressure, but a further 5.6 million are thought to be living with the condition undiagnosed and the test should help give such people an indication that they may be at risk.
Almost two million respondents have completed the test so far, and 78% have been found to have a heart age higher than their actual age.
Of those, 34% have a heart age five years older than their actual age and 14% are at least 10 years over.
Professor Jamie Waterall, national lead for cardiovascular disease at PHE, said: "Millions are at risk of cardiovascular disease but don't know it, putting themselves at real risk of suffering ill health or dying younger.
"Knowing your heart age is a simple way of finding out whether you're at risk of a heart attack or stroke. By making important lifestyle changes you can reduce your risk before it's too late.
"Taking a Heart Age Test is something you can easily do at home, but it could be one of the most important things you do to help you live a healthy longer life."
According to the latest figures from the British Heart Foundation, the death rate from cardiovascular disease has fallen by more than 75% since 1961.
But it still causes more than a quarter of all deaths in the UK, with people who are overweight, drink too much alcohol, and do not exercise among those most at risk.
Simon Gillespie, chief executive at the charity, said: "Millions of people in the UK are unknowingly living at high risk of a heart attack or stroke due to their lifestyle, their family history of heart disease, or undiagnosed conditions including high blood pressure and cholesterol.
"Our message today is that it's never too late to change. Take the test, and if you are concerned by the age of your heart, make an appointment to see your GP."