Supplements like magnesium, B12 and Vit D can be tested for.

If a person is deficient, then they can be replaced and the PN will stop and/or improve. But this is one small aspect of PN.

The really difficult primary causes have no cures. The drugs, toxins, heavy metals, etc often leave a long term result.

So little is known about healing PN, that it is difficult to understand the process, and that is why doctors do not engage the subject at all.

Things like lipoic acid, work well for diabetics. It MIGHT work for some others, but impaired glucose utilization is the primary target. Acetyl Carnitine helps damaged mitochondria work better, and this is not a cure either, but may offer some symptom relief as long as it is taken. (HIV drugs, and other toxins may damage the mitochondria this way...but that is a theory). Benfotiamine works well for diabetics or those who have a genetic error in thiamine processing and utilization.

Malnutrition or malabsorption is not really a disease process, but more of a symptom. Once the person regains what is needed, the symptom (PN paresthesias etc) go away. It is difficult to know if a paresthesia is a symptom or a real nerve process. That is why all the testing is done. For example, anxiety and hyperventilation can give some dramatic numbness and tingling, just like damaged nerves behave. So there is a line of sorts, between paresthesia and PN...the word neuropathy means disease of nerves.
Poor circulation can damage nerves... like intermittent claudication (starved for oxygen). Fix the blood flow and the nerves return to normal functioning.

PN is very complicated... the supplements are only for some of the PNs, and not all. That is why we continually remind people that they have to become their own detective of sorts. The more details on your history, when it started, what was happening to you then, what food you eat, drugs you take, injuries you have, or extreme lifestyle like strenuous exercise or whatever, hobbies (solvents paints, etc) all play a factor in figuring it out. Sometimes this history is more useful than the fancy medical tests. And it can point to what you can do to try to improve your situation.