I was recently diagnosed via a blood test, that my Vitamin D level is 14.5. My doctor put me on a 50,000 IU of Vitamin D, once a week. I am wondering how long it will be before I have a clearer brain, and have less sadness. I am actually a very happy person, as I exercise alot, but I can become sad quite easily over certain things. I am a woman in my 50s.