ABUJA, Nigeria — President Muhammadu Buhari of Nigeria, who has urged politicians not to go abroad to seek medical care, has traveled to Britain on his fifth official trip to see a doctor there.

Mr. Buhari, 75, left for London on Monday for a four-day visit, setting off renewed concerns about his health. His trip also comes after three weeks of strikes by health care professionals who are calling for better working conditions and more funding.

For nearly two years, Mr. Buhari has been receiving treatment for an unspecified illness, which he has repeatedly refused to discuss.

The president is scheduled to return to Nigeria on Saturday, at which point he will have spent more than 170 days in London on official medical leave since becoming president in 2015.