Vitamin D question

Hi
I had a lot of Thyroid test done some came back ok some others"ah not as good" but I need help because my results also say i'm Vit d "low" I think my result was 19 but to sure right now.Anway what vit d should I take
Vit d3 I heard is the best,I sure pray I don't have an absorbtion problem going on because I have take a seizure med
for 32 yrs because I fell out of an auto when I was 3 and had some brain damage from it.I'm to also ask the endo to check andrenal panel and pituitary mri and Thyroid scan.Is their any other tests or hormones I should ask to have tested.? I had a lot of the Thyroid  but not ferritin or cotisol.But any way help with the Vit d and advice on anything else you all think would help.Thanks Shirl