Refugees and other migrants receive a lower standard of health care in the countries they arrive in than do the local residents, the WHO reported in Geneva.
The World Health Organization also said on Wednesday that migrants on average had a poorer level of health, and that this was not down to being naturally less healthy than the locals.
Apart from language, cultural and legal barriers, other factors negatively affecting migrants and refugees included education, income and living space, it said.
"Today there are some 1 billion migrants globally, about one in eight people," WHO Director-General Tedros Adhanom Ghebreyesus said. This included internal migrants – those who moved from their homes but remained within the country.
"The experience of migration is a key determinant of health and well-being, and refugees and migrants remain among the most vulnerable and neglected members of many societies," he added.
According to a meta analysis of 17 million participants from 16 countries, evaluated by the WHO, migrants go to the doctor less often and often carry work-related injuries.
A significant number of the estimated 169 million international migrants – those living in other countries than their home country – work in dirty, dangerous and stressful jobs. They are at greater risk of accidents at work or health problems directly attributable to their work, such as working with hazardous substances.
The WHO called on host countries to collect better data on population health and to invest more in the health sector. It pointed to the huge contribution made by migrants during the coronavirus pandemic, with up to half of health staff in the richest countries coming from other countries.
