I do know that a normal range for Vit D3 is above 50 at least. If you are being tested for Vit D3, make sure the right test is being done. Being low in Vit. D causes tons of problems, especially cancer concerns. Do some research and then TELL the doctors what you want and make sure that you get the answers you want. I supplement with D3 in the fall/winter months with 4000-5000 ius of D3 daily. I was 54 after being tested last time. So good luck and help yourself by doing your homework, trusting the next guy isn't always the way to go. Good luck