 So Dr. Pincus, what makes your Fastmelt vitamin D formula so unique? Well, Chris, first of all, I put 5,000 units of vitamin D3 per serving in each tablet so you can actually feel the difference. I wanted to give you enough dosage so it really goes to work. Second, I use the right type of vitamin D in my formula, which is superior and readily available so your body can digest it, and this is known as vitamin D3.