Some vitamins have kosher sensitive ingredients or outright treif (gelatin) you need to ask a competent rav. Many rabbanim will matir it if medically necessary. Many vitamins are available in kosher.
Maxi health makes quality products. You need to be careful with supplaments that they’ are good quality and necessary. Taking to much can be harmful. Example excess of b range vitamins can cause an increase in the need for the other ones. Too much iron can cause GI upset. Too much vitamin a can cause hair loss.
There are a lot of examples but I will leave that up to your medical professional.