If you are found to be eligible to take part in this study, you will begin receiving doxercalciferol. The dose you will receive will be based on how many participants have been enrolled before you, and on the safety data that is available. You will remain on the same dose level throughout this study. There will be up to 9 participants enrolled in each group of the same dose. The first group of participants enrolled on this study will be given small doses of doxercalciferol. If no intolerable side effects are experienced, the next group of participants will be enrolled at a higher dose level. This process will continue until researchers find the highest tolerable dose of doxercalciferol, among the 5 dose levels being tested, that can be given without intolerable side effects occurring.