A new study finds many people have high blood pressure and don't know it. Also, many of those who are already on medication to get their blood pressure under control are not doing a good job of it.
Mcmaster University researchers in Hamilton, Canada looked at more than 140,000 people from 17 countries.
They found 40% of people in the study had high blood pressure, but nearly half of them didn't know it.
Of those who were aware of the diagnosis, nearly 88% were on blood pressure medication, but only a small number of those receiving treatment had their blood pressure under control.