Can I use minoxidil 5% to grow hair and stop when my vitamin D levels get back to normal?

If your hair loss is being caused only by a vitamin D deficiency, then correcting the deficiency in most cases is enough to stop the progression of the hair loss. If that is the case, and there is no component of genetic hair loss present (or any other cause of hair loss) then you probably don't need the minoxidil. But oftentimes, there is also a component of genetic hair loss or other cause present as well. In reality, when a patient comes in with hair loss and we find abnormalities in their labwork, we cannot say for sure that the hair loss is definitely being caused by that and that alone. If the hair loss is distressing enough for the patient, I usually recommend correcting the lab abnormality but simultaneously starting a preventative regimen. This would consist of finasteride (if you are not a woman of childbearing age), minoxidil, Low Level Laser Therapy and PRP procedures. Using topical minoxidil alone might be helpful but its best if used as part of a more comprehensive hair loss prevention regimen. If you have a component of genetic hair loss present, then you would want to continue these things even after your vitamin D levels have been normalized.