My b12 was chronically low but it manifested in thinning hair, low energy and pins and needles
Doctors ignored me for 20years and it was only because I had a telephone consultation during Covid that a doctor recognised the symptoms
Three years to get to such a low b12 level is unusual. Especially as they were supplementing at least for some of the time
Of course very low b12 can cause depression and paranoia.
How incredibly sad !