An aide to Lebanon's top Shi'ite cleric says the influential sheik is currently in the hospital for a medical checkup.
Three months earlier he successfully underwent a minor procedure measuring the flow of blood to the heart.
Grand Ayatollah Mohammed Hussein Fadlallah "is well" said his aide Hani Abdullah.
Fadlallah, 74, is one of the most influential Shiite clerics in the world with strong followings in Lebanon and Iraq.
Western media has called him the spiritual leader of Hezbollah, a claim that he and the group deny.
Fadlallah, a harsh critic of US Mideast policies, is known to suffer from diabetes and high blood pressure.
He was born in Iraq and 30 years later moved to Lebanon. Shiites make up one-third of Lebanon's population.