My hair isn't as thick as it used to be... I would like to know the effectiveness and treatment cycle for hair loss.

I am losing more hair when shampooing, and when I take photos, the crown of my head looks much thinner than before, so I am considering hair loss treatment for the first time. I am a bit hesitant about taking oral medication, so I am thinking of starting with treatments like scalp injections or laser therapy. When reading descriptions, I see terms like "follicle injections" and "scalp injections" frequently, but as a layperson, I understand them simply as procedures that inject nutrients into the scalp to make the hair thicker.

My main concern is the effectiveness and frequency of hair loss treatments. I’ve heard that treatments aren't usually a one- or two-time affair; instead, you receive them several times at intervals of two weeks to a month to see gradual changes. However, I am curious how many sessions it actually takes to notice changes in hair density or thickness. I also want to know if it is common to start with frequent treatments and then switch to maintenance treatments once a month or every few months later on. Since my crown is my biggest concern, I would like an explanation on what kind of results I can expect based on that area, and how to realistically plan a treatment cycle of three or six months.