I highly recommend this product. I started taking it back in May 07 after going through another dark Chicago winter, being diagnosed with cancer, and learning I was Vitamin D deficient. I have taken one capsule a month ever since, and in times of stress or illness I take an extra one in the middle of the month. I have never had excess levels of calcium, and in fact right now I'm low on calcium so I make take more of this. For healthy individuals it is fine to take once a month, just my opinion, if you get sick a lot or work at a highly stressful job and don't get out in the sun much or drink much milk, I would take it at least that much or maybe every three weeks depending on your situation. And if you don't believe me, look at this article from the NY Times showing the research that Vitamin D protects against major diseases AND that the lack of it is linked to major diseases- as it was to mine. [...