I've wondered how low it goes too. My reading in spine is about -3.5. I hadn't seen a lower measurement, so thought maybe -4 was lowest! Also, a physical therapist told me they never got patients with lower readings than mine. Huh. I'm still functional, although my back aches every afternoon, and I can hear it creaking when I exercise, (carefully).

I have -6 osteoporosis in spine.
I rest every day when the pain comes on. I try to exercise & live with family.