Great graph. Before seeing it, I concluded getting it to 32 ng/ml is a good goal, because when we reach that level, the body starts inactivating Vitamin D.
People take too much Vitamin D. For a long time, people in cold countries took 10 micrograms per day.
For an experiment, people took 100 micrograms per day for a few months. Their blood level was 67 ng/ml. People with 50 ng/ml have more kidney stones.
Groups at higher risk for the wuhan coronavirus have more stored iron.
You also need vitamin k2