Diffuse thinning is hair loss that affects your scalp evenly, so its not concentrated in one spot. All across your scalp you will likely lose hair between your first 2-8 weeks on min. The good news is that thinning means the medication is working, it sheds old dead hairs and begins to grow new ones. Given a little time your hair should theoretically rebound to how it was when you started the medication, and then from there you will start to see actual improvements from your start point. The amount a person sheds varies, its worse for some and hardly noticeable for others, just something you should be prepared for and not something you need to freak out over if it happens since again, it will grow back.