Nigerians spent $1bn (£690,000) on foreign medical trips in 2013, most of which was unnecessary, said Dr. Osahon Enabulele.
Nigerian politicians were mostly treated by Nigerian doctors in the UK, he added.
Buhari flew to London on Monday to be treated for an ear infection, the BBC reports.
It is unclear where the 73-year-old would be treated for what his office described as a “persistent” infection.
Dr. Enabulele, vice-president of the Commonwealth Medical Association, said it was a “national shame” that the President went to the UK for treatment when Nigeria had more than 250 ear, nose and throat (ENT) specialists, as well as a National Ear Centre.
“Buhari should lead by example by using Nigerian doctors and facilities, and ensure government officials do not go abroad on ‘frivolous’ medical trips, he told the BBC.
The UK had more than 3,000 Nigerian-trained doctors, and the United States more than 5,000, Dr. Enabule said, accusing the government of failing to address the brain drain by improving working conditions and health centres.