Sure but most people in the west have chronically low serum vitamin d levels. Proper D levels have a ton of other known beneficial effects including protecting against several types of cancer, proper calcium regulation, disease prevention etc etc.
The current recommendation is keeping serum levels at least above 30, and more like 40-60. Many many people aren’t in that range.
my doc orders the test every year at my physical exam. i'm not sure it would normally be included in blood tests they order for your physical (like cholesterol), at least in the US.
Improving sleep quality does not mean the same thing as alleviating symptoms of insomnia, exactly. It would appear vitamin D could improve quality in most people.
The current recommendation is keeping serum levels at least above 30, and more like 40-60. Many many people aren’t in that range.
https://pubmed.ncbi.nlm.nih.gov/32679784/