Did they say why you are deficient? I found out I have Hyperparathyroidism which causes vitamin D deficiency. My level was at 7 and I had to take 50,000 IUs once a week to get it back up. Now I take 6000 three times a week and 4000 every other day to keep them up. For some reason, a hyper parathyroid likes to suck it out of your body.

There are other reasons for it as well, and sometimes it's just a lack of sunshine and nutrition.. .just make sure you find out why so you're not going back and forth with it.