We have just started taking 10,000 IUs daily in our house as we are all decificient and nobody can handle that amount. We have severe headaches and body cramps that indicate a magnesium deficiency. So we began 500 mg of Mag Citrate. That helps, but the D3 still makes us all wired as if we had many cups of coffee! I have taken D3 in the past and noticed that 6,000 daily (plus the 800 IU from multivitamin) did not wire me up. I would like to go higher than that but it seems none of us can tolerate it.