I've been taking this for a month together with other multi-vitamins. Carlson Labs seems to be high quality from reviews from Labdoor, so I decided to trust this brand. Dosage is simple with just 1 pill. The pill size is small and very easy to swallow. I don't feel any immediate effect but from Doctor Berg's video (see Youtube), Vitamin D is essential to build up immunity which is definitely needed in this time and age.
I have been using this product for a few years with my doctor’s recommendation after my blood test showed low vitamin D level. T is easy to swallow. Effective as my vitamin D level went up to a normal after a few months