I had a blood test for Vitamin D levels a few years ago. I was very deficient. Very. My doctor prescribed 50000 iu prescription dose 1 x per week + 2000 iu 2 x per day D3 (over the counter). My blood levels were checked frequently. It took a full year of this before my blood levels of Vitamin D reached the lowest minimum level. I no longer take the prescription D. I do continue to take OTC Vitamin D3 and have blood levels checked annually. Vitamin D seemed to help my moods and my energy. By all means, talk with your medical professional, do research, and make your decisions based on your situation.