It’s not common at all to have low copper levels, sorry this might be long from what I have read and from what my neurologist suggested I have something called myeloneuropathy which is when the copper deficiency presents it’s self as a type of neuropathy. It’s uncommon/ rare to have true copper deficiency which means there’s a low amount in your blood( circulating through/ what your body is currently able to use.) and a low amount tested in pee ( meaning there no extra and your body probably has low/ none stored up.). It takes zinc over dose/ or underlying condition like malabsorption or having a reaction to a certain type of surgeries. Copper added into a lot of cereals and stuff like dark chocolate, one bar or dark chocolate is like 300% of the recommend copper intake for a day. Copper causes neuropathy because it’s a main component of spine health from whagni was able to understand from the study Mayo did. I also did read about punch biopsy’s but I’m unsure if that would be helpful or not, I’m sure it would show up abnormal but my doctor would just say it’s because of the copper and of B6 deficiency and tell me to keep taking supplements that make me throw up. Also please don’t over worry or stress about copper levels only about 10% of people have a true deficiency every year and it’s usually caught because people become anemic and have no clear reason to be.