Is a חולה שאין בו סכנה allowed to take vitamins that are not kosher for Passover
In general vitamins are considered a dietary supplement, and not a medicine. Therefore, you should make sure that the vitamins that you take are kosher for Passover, as they may contain chometz or kitnios. If there is a specific need and a specific condition, that would have to be assessed on an individual basis.
Have a chag kasher vsameach.
Teshuvs Vhanhagos 5-127, Ohel Yackov (Kashrus L’pesach) pg. 222 ftnt. 11.