High blood pressure can be hidden for a 'considerable' number of cases among young people in England, research claimed.
About 170,000 of people aged 16 to 24 could unknowingly have the risky condition, which can lead to serious health problems.
This is equivalent to five in 100 young men and one in 100 young women, according to the Office for National Statistics (ONS).
High blood pressure, also known as hypertension, is one of the main causes of heart attacks and strokes – responsible for half of cases in the UK.
Contrary to popular assumption, it can develop at any age and might not cause any symptoms to begin with.
This means the condition can often go unnoticed, despite putting extra strain on the blood vessels and heart.
The ONS carried out the new research in a bid to find out which groups are most at risk of having undiagnosed high blood pressure.
Chris Shine, from the analytical hub, said the findings will give valuable insight for tackling what is "one of the most common causes of premature death" with young people of particular concern.
"We see that there are considerable numbers of younger, healthier people who are undiagnosed," he told the BBC.
"It may be that this group are unaware they have the condition because they are less likely to access healthcare if they are otherwise well."
"The sooner hypertension is identified, the more effectively it can be managed and treated among all ages."
Young men are particularly likely to be undiagnosed, according to the ONS study.
Two-thirds of men and around one-quarter of women aged 16 to 24 are likely to be undiagnosed.
This is also the case for 55 percent of men and 44 percent of women aged 25 to 34 – a stark contrast to the 17 percent of men and 21 percent of women aged 75 and over.
Around one in three UK adults have high blood pressure, but experts say many do not know they have the condition.
Some of the main factors that raise blood pressure include an unhealthy diet, drinking too much alcohol, being overweight, not being active, and smoking.
The findings come from the results of at-home blood pressure measurements taken from 20,000 people, including 1,500 young people, for the Health Survey for England.
Overall, it suggests around four percent of women and seven percent of men aged 16 to 24 have high blood pressure in England.
Within those said to have the condition, 26 percent of women and 66 percent of men were undiagnosed.
Symptoms of high blood pressure
It is very common for people with high blood pressure not to experience any noticeable symptoms for some time and it is important to get regular blood pressure checks, according to the British Heart Foundation (BHF).
But on the rare occasions the symptoms do rear their heads, here are some signs to look out for:
- Blurred vision
- Nosebleeds
- Shortness of breath
- Chest pain
- Dizziness
- Headaches
The BHF advises: "Many people with high blood pressure feel fine. But even if you feel fine, you should still have your blood pressure checked regularly.
"If you're a healthy adult over 40, it's recommended that you get it checked at least once every five years.
"But if you're at increased risk of high blood pressure, you should have it checked more often, ideally once a year."
How to check your blood pressure
GP surgeries are able to check your blood pressure along with some pharmacies and even workplaces.
Those aged 40 to 74 in England can ask for an NHS health check with similar schemes available in other parts of the UK. Doctors should write to you about this every five years but you can also book an appointment for more regular checkups.
