I spent two years following the doctors recommendations on dosage, and my number never got above 20, even when taking 10,000 iu a day. They were recommending 800, then 2000. Very very conservative and obviously not enough. I felt so rotten my doctor finally caved and prescribed the 50,000 dosage twice a week (I have some weight to lose, which isn't helping my absorption. I would start with only 50,000 weekly unless told otherwise).
A tip: Instead of filling the prescription at the pharmacy, where it was $1.00 per pill, I ordered a bottle of 100 off Amazon for about $16.00. Vitamin D3 requires no prescription, so even the high dose are available over the counter. I just got my number back today after taking it for 4-5 months, and it is 63!
Personally, I would try to get that number up a little higher. If you have access to a doc who will order a blood test, try 10.000 iu for a few months and then check. The difference in functionality is huge, and like a previous poster said, who knows what damage was done that I could't feel all that time.