Health going to Doctors

We are required, to seek medical advice, and receive medical treatment.
But in addition we have to recognize, that illness and recovery, are dependent solely upon the Almighty; and that doctors medications we use work only, as His faithful messengers in granting us good health.
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The Gemara says in Masekhet Aboda Zara, that just before a person takes ill, G-d announces how long the illness will last, and through which means it will be cured.

This emphasizes the point, that only G-d determines when and how our health is restored; even though, as a practical matter, we are required to visit doctors and undergo medical treatment. We must avoid the misconception, that the physician or the medication, has the intrinsic power to cure our ailments.
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The Sages teach, that long ago there was a book called Sefer Harefu'ot, which listed all the ailments from which people suffer, and the remedies to cure them.

This book was transmitted from one generation to the next, until the time of the Judean King Hizkiyahu, who buried it.

Hizkiyahu saw, that people were responding to illness, by simply following the instructions in the Sefer Harefu'ot, without repenting or turning to G-d for assistance. He therefore felt it was necessary to hide the book, so that people would remember, to look to the Almighty as the exclusive source of healing.
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The Sitz Eliezer adds in this context, that sometimes G-d brings sickness upon a person, as punishment for a transgression; and in some instances, the purpose is for the patient, to incur a financial loss, and thereby earn atonement.

Illness often results in medical expenses and loss of work, and this financial loss serves to atone, for a person's wrongdoing.