And a new poll suggests that 55% of eligible men and 53% of eligible women have never been invited for the "vital" check-up.
The survey of 7,407 adults in England, conducted by Savanta, found that around three in five had attended every health check they had been invited to - 62% of men and 60% of women.
People aged 40 to 74 without any long-term conditions are supposed to be invited for an NHS Health Check every five years.
During the check-up a health worker will assess if a person is at a higher risk of certain conditions including heart disease; diabetes; kidney disease and stroke.
Those over 65 will also be told about symptoms of dementia.
The Department of Health and Social Care said over the last five years three quarters of eligible people were invited for an NHS Health Check.
"The NHS Health Check is a vital prevention tool, but it only works if people are invited, understand its purpose, and feel motivated to attend," said Louise Ansari, chief executive at Healthwatch England.
"Our research shows we must ensure that everyone eligible for the Health Check receives an invitation and is given clear information on why it is important.
"Key to this will be using trusted sources like GPs to reach those most at risk."
Healthwatch England highlighted how the NHS Health Check is funded through public health budgets and claimed that due to reduced funding, local authorities and GP services have "deprioritised" it in recent years.
It has called for the Government to collect and publish data on who is being invited for the check-ups.
The poll also revealed inequalities in access to the health check with 32% of men living in towns and cities saying they have been invited for a health check in the last five years compared to 21% living in the countryside.
Healthwatch has called for specific action to be taken in the upcoming Men's Health Strategy.
It says the consultation on the strategy names cardiovascular disease as a priority for improvement.
"The new Men's Health Strategy is a crucial opportunity to get this right - and prevent thousands of premature deaths from cardiovascular disease," Ms Ansari added.
A Department of Health and Social Care spokesperson said: "Over the last five years more than 75% of the eligible population were invited for an NHS Health Check.
"We are actively improving this vital programme that catches people at risk of heart disease and stroke early, by developing an online check that people can use at home, at a time and place convenient to them.
"We're also acting to prevent cardiovascular conditions in the first place by tackling smoking and obesity, and through our 10 Year Health Plan we will turn the NHS around by shifting the focus of care from sickness to prevention.
"Alongside this, our forthcoming Men's Health Strategy will also seek to improve the health and wellbeing of all men across England, including improving outcomes for health conditions that hit men harder."
