Someone wrote this on a forum I was reading about vitamin A and vitamin D deficiency. So, it does not mean it is accurate information. I just thought I would share it.
"The "Adequate Intake" value given to us of VitD by our dangerously inept at nutrition government is at 200, so they're only off by a factor of 20... Apparently the only recorded case of toxicity from VitD supplementation was the result of a manufacturing error whereby pills contained over 400x the labeled amount and resulted in a man taking between 150,000 and 2,000,000 IUs every day for almost 2 years. The man fully recovered. Vitamin D is necessary for the proper genetic expression of over 200 different proteins so you will probably only experience a side effect of better health/athleticism/respiration/etc. "