I’ve been toying with idea of upping vitamin D Iu. Currently its 1000 and that was what was prescribed to me a while back.
The nice thing with vitamin D is that you can actually check its level in bloodwork. The normal range is often considered to be between 50-125 ng/mL with below 30 considered deficient and above 120 or so considered too much.
I highly recommend people stay on top of this particular vitamin. In addition to evidence that a deficiency significantly affects your immune system functionality, it’s also uncomfortable. My spouse has been deficient in the past and experienced hand cramps, back spasms, muscle aches etc.
It’s fat soluble so it takes a few weeks to get it back to normal after supplementation
The conclusion of my study was that we should do more studies where we take regular blood level samples and adjust dosage to achieve a certain average level (near the upper level of the range).
5000IU D3 (D2 is about 1/3-1/2 as effective at raising blood serum levels) is a good starting point.