This is an answer for all of you! You can make up your own mind between D2 and D3 if you just read about it online. Just put it in your browser (search engine) "Benefits of taking vitamin D" and you will begin learning. But yes, someone who specializes in osteoporosis will definitely tell you about D2 and D3. The 50,000 IU dose of D2 is partly because it is so inefficient. 2,000 IU of D3 per day will do the same thing. Everything I say should be checked and double checked with your doctor. You know your own body better than anyone. The 50,000 IU dose of D2 used to be used for people with multiple sclerosis. JK - there IS somebody out there who is testing supplements - it is http://www.ConsumerLab.com. They do laboratory tests on supplements and they post their findings. They test the purity of supplements, they test the strength, and they test to be sure they will open up in your body (some pills go straight through you!). I once soaked a turmeric pill in warm water (it was warm when I started) and it didn't come apart for days - I finally gave up on it. This is why I know AlgaeCal only has 87% of the magnesium it says it has and it also has more than the allowable amount of lead in it! You can get a membership to ConsumerLab.com and read about any supplement you decide to take because they post many articles from medical journals for you to read - but of course, you still need to run it past your transplant team. Lioness, I actually was taking collagen in just plain water there for a while. I will make myself a smoothie yet. I am on a no-sugar diet as I've said many times, and I found a good recipe for a smoothie in the book that goes with my diet, "The Candida Cure," by Ann Boroch. Lucky me, I have to get a very long MRI with and without contrast tomorrow in San Francisco, so I have to get up early (that pituitary tumor had better not be back!). So I am going to sleep early. I wish us all good luck with our bones. Keep up the good work everybody! And let us know how you are doing.