Is thinning hair also a symptom of hair loss?

Lately, I'm worried because my hair seems to have lost its strength and become thinner overall compared to before.
In the past, when I tied my hair up, it felt quite thick, but these days, when I tie it, it feels like the hair tie wraps around one more time, and the crown of my head is slightly visible.
It doesn't seem like I'm losing a lot of hair, but I'm more worried about the change in thickness.
In this case, would it be a good idea to get a hair loss test? I'm curious to know what tests those of you who started with similar hair thinning have had at the hospital!