The king was admitted Wednesday to the National Guard's King Abdulaziz Medical City hospital in the capital Riyadh. The statement did not disclose further details.
The 90-year-old monarch appeared before the press this year in a wheelchair with an oxygen tube. He reportedly underwent surgery in late 2012 for his back.
Abdullah officially assumed the throne in 2005, but had been the de facto ruler of Saudi Arabia since the mid-1990s.
His successor is half brother Crown Prince Salman. Abdullah has outlived two other half brothers who held the crown prince post.