From research around the Internet, D3 is generally seen as safe (<a href="http:&#x2F;&#x2F;www.mayoclinic.org&#x2F;drugs-supplements&#x2F;vitamin-d&#x2F;safety&#x2F;hrb-20060400" rel="nofollow">http:&#x2F;&#x2F;www.mayoclinic.org&#x2F;drugs-supplements&#x2F;vitamin-d&#x2F;safety...</a> is pretty typical on the safety information) Personally I take a D3 supplement of 2000IU&#x2F;day during the dark months (along with some other supplements due to a mostly vegan diet, some of which contain low D2&#x2F;D3 amounts, so my actual supplemented intake is around 2400 IU).