2Chron16:12-13 has King Asa dying of a disease because he relied only on doctors and didn’t seek the Lord (the last part of his reign he became an enemy of the Lord). A corresponding New Testament is Mark 5:26-34 where the woman who was injured by the doctors sought healing from Jesus and was healed.
Some healings are beyond the realm of any doctor’s help and one has to seek a remedy from Jesus or no healing will happen.