Is this a symptom of orthostatic hypotension?

The test results showed that I have no anemia and no particular problems (I had a health checkup. I added all the additional tests).

I often experience moments where I suddenly feel faint or my vision goes black whenever I sit down and then stand up.

In those moments, when I feel like I might faint, I just sit down right there or close my eyes and stand still.

If I just stay like that for a few seconds, I feel okay and go back to my daily life.

I had fallen a couple of times, but I think I regained consciousness within a minute.ㅡㅡ

Is this symptom orthostatic hypotension??

Then, what kind of test should I take and how should I do it??

Please recommend helpful dietary supplements.