How long do I have to wait to see results after starting hair loss treatment?

While recently researching hair loss treatment methods, I learned that there are various options available, such as medication and scalp treatments.

However, since I don't think changes will appear immediately after starting treatment, I am curious about how long you take to assess the effectiveness.

For those who actually started treatment, what criteria did you initially use to monitor your progress? I would also like to know if you periodically compared photos or test results.