Vitamin B12 Deficiency - American Family Physician

This link which is for doctor's to learn new medical information, explains how the new low for B12 should be 400pg/ml.

Many labs still report lower than 400 as "normal" and doctors
tell patients they are normal for B12 and hence the damage continues and patients decline.

This is very common, low B12...so it is important to find out your exact test result.

There are over 100 causes of neuropathy, so finding out what is causing yours may be important, because you could avoid something toxic to you and then enhance healing up with some supplements.

Some drugs that doctors give patients (statins for cholesterol lowering and fluoroquinolone antibiotics like cipro and others)
can damage nerves too. Virus infections, and vaccines can be triggers as well.

How old are you? What was going on before your first attack?
Do you do extreme sports or gym routines? Nerve compressions in the spine can give neuropathy symptoms. Are you exposed to solvents? The list can go on and on.

To get answers you have to tell us more details. Sometimes it is diet (pre-diabetes, gluten sensitivity) are possible triggers.