Taking two booster doses of the coronavirus vaccine, without medical advice, after being fully inoculated could pose a health risk.
Some residents have tried to take extra booster shots for travel purposes, it is understood.
People who received the Sinopharm vaccine could be eligible for a third shot, but some have sought to get a fourth for travel purposes.
"We note that some people may insist on taking more doses of the Covid-19 vaccine than recommended, which contradicts the opinion of doctors, and which may expose them to unwanted health complications," an official said at a government media briefing.
"So we advise everyone to adhere to the opinion of the treating doctor in order to ensure their health and safety."
In Abu Dhabi, the authorities require a GP's medical assessment before they administer a booster shot.
In Dubai, this is not required and people attending clinics are asked to be honest about their vaccine status.
People planning to travel to Europe this summer would not be eligible to enter some EU countries if they had taken the Sinopharm vaccine, which is yet to be approved by the European Medicines Agency.
That has led some people to try for two Pfizer booster shots to secure the necessary vaccine card.
Asked about people taking two Pfizer shots after Sinopharm, Dr Farida Al Hosani, a federal government health spokeswoman, told The National that all residents must "check their eligibility to receive the vaccination based on the medical evaluation" set out at the vaccine centre.
Boosters should be taken based on medical need and not for any other reason, she said.
Clinics have also offered a third dose of the Sinopharm vaccine for those who had a second dose six months earlier.
Meanwhile, the government on Sunday said that one in three Covid-19 cases in the UAE are of the highly infectious Delta variant.
The number of deaths in the country increased and this was attributable to the spread of mutations, not following rules and failing to take the vaccine, officials said.
Ninety-four per cent of deaths occurred in unvaccinated people. Only 6 per cent of people who died had received the vaccine.
The figures were released on Sunday during a Covid-19 briefing, at which the authorities stressed the importance of being fully vaccinated to ensure full protection.