The Billy Graham Evangelistic Association (BGEA) says the 97-year-old is, nevertheless, still obeying God's calling for his life and prays for the UK "everyday".
UK Director of the BGEA, Steve Wade, said: "He really did come through [a] sticky patch and he has been well in himself for three or four years now - he is just very frail.
Vancouver Christians excited to see Christ work through the Festival of Hope https://t.co/NeDRhaliXH #BGFEST pic.twitter.com/Ld4RaconzH
— Billy Graham Canada (@BGEAC) August 11, 2016
Mr Graham is perhaps best-known for a series of evangelical public speaking events around the world, the first of which was the 1949 Los Angeles Crusade.
He has shared the Gospel almost 215 million people in more than 185 countries and territories, meaning he has spoken to more people in live audiences than anyone else in history, the BGEA says.
Steve Wade added: "How can we pray for Billy? Just pray for strength as you continue praying.
"Pray for us as an organisation that we will honour the incredible legacy of an incredible man of God and that we're faithful to all that he stood for and the integrity he's stands for, in the way that we work with everybody across the UK and worldwide."
In statement Franklin Graham recently shared on his father's health said: "Many ask about my father. He is still in his own home and often eats meals at the kitchen table, as he has always done. Approaching age 98, he lives with limitations typical of old age—his eyesight is very poor, his hearing is not good, and he uses a wheelchair. Someone is with him in the house at all times.
"One of the things he enjoys is sitting on the front porch and looking out over the mountains on days when the weather is good and he feels up to it. He watches news with the help of a large-screen TV. His ministry now is praying, and he looks forward to reports of what God is doing around the world. He always responds by saying "Praise the Lord" as he points upward."