Africa has the highest rate of high blood pressure in the world, affecting about 46% of adults, a World Health Organization (WHO) study has found.
It blamed increasing urbanisation and unhealthy lifestyles for the rise in cases.
The global average for the number of people suffering from the condition was about 40%, the WHO said.
High blood pressure was often detected too late and was a silent killer, it added.
If lifestyles do not change, more people in Africa could die from chronic illnesses, including diabetes and cancer, than infectious disease by 2030, the WHO said.
The report's author, Abdikamal Alisalad, said the level of unhealthy habits in many African nations had come as a shock.
"We were surprised because we thought we would not see this kind of situation currently. We were expecting it maybe 30 or 40 years from now," he told AFP news agency.
He attributed the rise in non-communicable diseases to changes in developing societies.
"People are moving from the rural areas, going to urban, metropolitan areas. The middle-income group is growing, life expectancy is also growing."
Of the 34 African countries surveyed, Ghana, Nigeria, Seychelles, Cape Verde and Sao Tome and Principe had the highest prevalence rate of high blood pressure.
Treating non-communicable diseases is costly, so it is in the economic interest of every country to support prevention campaigns, says BBC Africa health reporter Anne Soy.
Experts recommend eating at least five servings of fruit and vegetables a day, quitting smoking, drinking in moderation, reducing salt intake and exercising often.