Some vitamin D supplements were tested by ConsumerLab.com to determine whether they contained the claimed amount and form of vitamin D, calcium and vitamin K, were able to disintegrate fully to be available for absorption, and if they were free from unacceptable levels of lead.
This may not be news to you but: The most common problem found with the supplements containing vitamin D was the wrong amount of vitamins. For example, a tablet listing 800 IU of vitamin D contained only 664 IU, 83 percent of the listed amount. Guess this is kind of common problem but what can we do.
I've never had much faith in those med companies and to be honest this doesn't do any good for that. If I want to find something positive about this: at least they didn't put more vitamins than claimed. It can be hard to stay on track how much e.g. vitamin D you get from food and fortified milk. Although it shouldn't be much of a concern because it seems that we should get much more vitamin D than we're suggested. I've read about the recommended amount being 50 mcg/day for real which is over 5 times than we are suggested at the moment where as the tolerable upper intake level being about 100 mcg/day.
You can view the whole article here.