I have been taking Vit d Daily at a dose of 1000iu. I know that there are IM shots of Vit d. How are these shots dosed? weekly? monthly? And how are they absorbed? Like if I take 1000 a day, would the shot then be 30,000iu one shot per month? Or does it degrade faster than that, say I need 60,000 units to get the same results?