I have been taking a relatively high dose of Vitamin D since April 2016 when I was being diagnosed with Multiple sclerosis. After blood work, my results came back well below 'normal' standards, where I believe I was around 9. I was prescribed 8,000 units of Vitamin D for the first several months, then moved to 6,000 units and now after 2 years take 5,000 IU. One pill of this suffices, which is great since I do take other medicines at the same time. I periodically have my blood drawn and checked for my Vitamin D level and per my results I just got back, I am at 48 (speak with your physician, but I believe recommended range is 30-80). I have not taken any other brand of Vitamin D because after several tests, I know it is increasing my levels. I will continue to use this and will recommend the brand. I have tried the small tab version and it is too hard to swallow and gets stuck in my throat. These are slick gel and are easy to take