I require Vitamin D daily due to my oestoporosis diagnosis at the age of 50. I have used another brand previously for several years and all my monthly blood tests have been in the correct range for calcium levels. When I saw the Swisse brand on sale, I was keen to try it. The brand has also been endorsed by athletes and sporting competitions. So, I was extremely disappointed after spending a considerable amount of money for the large bottle of Swisse Vit D, to be told by my GP after my next routine blood test that my calcium levels had dropped to below a recommended level. In fact, they were so low now, that I had to go back to my old brand and start taking 2000iu daily instead of 1000iu. Very disappointing!