Concur: that would be surprising. I was more focused on the possibility of having a dangerously high blood level which is fraught with negative sequelae.
This test — among many others — offer quantitative results at home:
Pretty expensive though. Lab costs in Germany are <20 € for a quantitative test and the cost of the physician for taking the sample is usually covered by insurance.
This test — among many others — offer quantitative results at home:
https://empowerdxlab.com/products/product/VITD?gad_source=1&...