Presidential spokesperson, Femi Adesina, said only God has the guarantee over such matters.
The president is scheduled to leave Nigeria on Tuesday, May 8, and head to London to meet his doctor for a medical appointment that is scheduled to last for four days.
While speaking about the trip in an interview on Channels Television on Tuesday, the president's Special Adviser on Media and Publicity, Femi Adesina, said there's no cause for alarm over the president's health as he's merely travelling for a medical 'review'.
When asked if the president will return to the country after the scheduled four days, as he's previously extended medical trips in the past, Adesina said only God has the guarantee over such matters.
However, he also noted that if all goes well with his doctor, the president will return to Nigeria as has been officially announced.
He said, "When you talk of guarantee, man cannot guarantee anything. Man cannot even guarantee life because somebody that is here in the morning could be gone in the afternoon; so in terms of guarantee, nobody can guarantee anything.
"But then, in terms of the health of Mr President, I'll just say there's no cause for alarm because he is up and about, he's doing his duties and what he's going for is a review. We all need that from time to time. There's nobody that is 100% healthy. He's just going for a review so I want to believe that he'll leave today and come back on Saturday as has been planned.
"But like I said, you know, it is only God that has a final authority on things but all things being equal, he'll be back on Saturday."
The presidential aide also dismissed quotes attributed to the president about putting an end to medical tourism during his tenure amid criticism of his frequent medical trips to the United Kingdom.
During the interview, Adesina also reiterated his position that the president doesn't have to disclose his ailment to Nigerians as he has a right to his privacy.
President Buhari is expected to return from his medical trip on Saturday, May 12.
In a statement released by Buhari's Senior Special Assistant on Media and Publicity, Garba Shehu, on Monday, May 7, the president's doctor requested his presence when he recently had a "technical stopover" in London. The president had stopped there on his way back to Nigeria while flying from a working visit to the United States.
Shehu said on Monday, "In the course of the technical stop-over for aircraft maintenance in London on his way back from Washington last week, the President had a meeting with his doctor.
"The Doctor requested the President to return for a meeting which he agreed to do."
President Buhari was missing from the public eye for two days before the presidency disclosed that he stopped in London because his plane was under repairs.
Shehu said on Thursday, May 3, "The big jet is under repairs. It has been taken for major repairs. So the president is using a small plane and there is a limit to the distance the small plane can cover.
"So the technical stopover I talked about is that the journey from US to Abuja is broken into two. Technical stopover is that the plane stops at a point, refuel, do some checks and then proceed on the journey.
Despite the presidency's claim, many media reports suspected that the president stopped in London to see his doctors, a theory that has now been admitted by the presidency.
In 2017, President Buhari spent a combined 154 days in London on two separate medical visits to treat an undisclosed illness, prompting concerns about how fit he is for duty.
Since the 75-year-old president declared to run for a second term in the 2019 presidential election, his health status is expected to be a major vulnerability for the opposition to exploit.