The accumulating troubles at length, in the autumn of 1504, threw Isabel into a tertian fever, which was aggravated by the fact that Ferdinand, being also ill in bed, could not visit his wife. Isabel’s anxiety for her husband was pitiable to witness; and though her physicians assured her that he was in no danger, his absence from her bedside increased the fever and threw her into delirium. Symptoms of dropsy, and probably diabetes, since constant insatiable thirst and swelling of the limbs are mentioned as symptoms, ensued, and for three months the Queen lay gradually growing worse and worse. Rogations for her recovery were offered up in every church in Castile, but by her own wish, after a time, this was discontinued, and the heroic Queen, strong to the last, faced death undismayed, confident that she had done her best, yet humble and contrite. When the extreme unction was to be administered she exhibited a curious instance of her severe modesty, almost prudery, by refusing to allow even her foot to be uncovered to receive the sacred oil, which was applied to the silken stocking that covered the limb instead of to the flesh.
To the last she was determined that, if she could prevent it, Joan and her husband should not rule in Castile as absentee sovereigns whilst Ferdinand lived. Her will, which was signed in October, is a notable document, showing some of Isabel’s strongest characteristics. She would be buried very simply, and without the usual royal mourning, in the city of her greatest glory, the peerless Granada; ‘but if the King, my lord,’ desires to be buried elsewhere, then her body was to be laid by the side of his. Her debts were to be paid, and many alms distributed and religious benefactions founded, and all her jewels were to be given to Ferdinand, ‘that they may serve as witness of the love I have ever borne him, and remind him that I await him in a better world, and so that with this memory he may the more holily and justly live.’ What does not seem so saintly a provision was, that all the royal grants she had given, except those to her favourite Beatriz de Bobadilla, were cancelled on her death. With a firm hand she signed this will later in October 1504, providing in it also that her daughter Joan should succeed her on the throne of Castile:[98] but before she died, almost indeed in the last act of her life, her fears for Spain conquered her love for her daughter. In a codicil signed on the 23rd November, three days before her death, she left to Ferdinand the governorship of Castile in the name of her daughter Joan; and enjoined him solemnly to cause the Indians of America to be brought to the faith gently and kindly, and their oppression to be redressed.