Fascinating. Maybe I'm misinterpreting your units, but I have no related health condition (other than living in Canada), and I take 3x1000 every day (in months with an R in them).
Maybe you're somewhere particularly sunny?
Stage 4/5 Kidney failure will do that unfortunately - it messes with your biochemistry.
ng? as in nanograms? 1000 nanogram = 1 microgram (mcg), 40 IU = 1 mcg.