A couple of things... In searching the archives for Australia methylcobalamin, I find many posts mentioning that iherb.com ships to Australia (I've never purchased from them so I cannot comment either way).

That search also turned up the following: (clicking on the > will take you to that post/thread)

Quote:

Originally Posted by Martin_12 A minor point: In the USA B12 is measured in picograms/mL (pg/mL)while in Australia the units are picomoles/L (pmol/L). According to the AFP paper by Oh you need to multiply Australian results by 4/3 or 1.3 to get USA values. So your 256 pmol/L is equivalent to approx 340 pg/mL in the USA. Wikipedia gives a similar conversion factor. Your value is still low. Make sure you are taking at least 1000 micrograms of methylcobalamin per day on an empty stomach as Mrs D recommends. I take 5000 micrograms/day. There are no known adverse effects of high doses. Martin

Any/all/none of the above.
One thing about PN that stands out (on this forum and elsewhere) is that it's a bit like fingerprints—no two people are (affected) exactly the same, though there are/can be similarities. The same can be said for spine issues. PN symptoms can also be affected by a wide range of variables (in addition to those you mentioned)—diet, time of day, hormones, endorphins, circulation, weather, et al.

Doc