With vitamin d, you need to get tested to see what your blood level is. When you get to a therapeutic dose in your bloodstream, you will no longer get sick with viruses and you will be preventing cancer and a host of other things.
I got tested in a hot summer month when I was getting sun exposure, and was already taking 2000 units of d3. My level was 25, far too low. I upped my dose to 10,000 units and after a few months, went back and my level was still too low at 45. I now take 15,000 units a day. A therapeutic dose brings your blood level up to 60. Maybe you only need 500 units.every human is different.
I see a huge difference in my energy levels and general outlook on life now that I’m on D3.