Vitamin D still low after 3 months of 4000 IU. Would you look into gut absorption?

Imported from Reddit r/VitaminD. Filed by the system importer, not a fake user. Original post: https://www.reddit.com/r/VitaminD/comments/1xtyc50/vitamin_d_still_low_after_3_months_of_4000_iu/ From the original post: Recently I (27M - 5ft10, 65kg) had a doctors Vitamin D blood results come back at 12ng/mL after around 3 months of daily 4,000 IU + K2 (That I was just doing by myself). I felt something was up before so got Vitamin D and I have noticed a positive difference - being more social, feeling more grounded, However I thought that being at 4,000 IU my vitamin D would have been much higher. My Dr has now prescribed me 20,000 IU to take once per week alongside my 4,000 IU. One thing to note is that I too