Does vitamin a lower vitamin d levels? i once used topical tretinoin for acne which led to hair loss. my vitamin d levels were borderline deficient at the time. was this because of the tretinoin? will supplementing vitamin d help my hair loss?

Topical applications of creams or lotions do not produce blood kevels of the agent that would interfere with the blood content of anything. Vitamin D deficiency is associated with numerous health problems but I don't recall hair loss as one of them. It is reasonable to assume it might.

Supplementing vitamin D would not likely help hair loss, but certainly would not hurt, but would monitor levels to be most precise. Typically, would aim for 50-70 ng/ ml, and would not go higher. Since it is fat soluble, it will take about 3 months to accurately assess the outcomes. Your doctor can help with this process.