Yes, and to be concrete, you can do so at economical prices at https://requestatest.com (it's a lifesaver in many occasions, I've used it 4 times with great success).

This is how I found my 10k IU of vitamin D a day, based on modern recommendations for indoor workers, that I modulate based on how much I'm outdoors, was perfectly on the mark!

My PCP uses Quest Diagnostics and a vitamin d test is, I think, about $50. No fasting needed for it, nor prescription.

You can get most tests (although often not genetic) in many countries, with Canada being an outlier in forcing you to get a doctor’s note for just about everything.