I am also low B12 and this is what I have learned about it.
30+% of the population is heterozygous (have one of the genetic defects) for the MTHFR defect, which has to do with the body's ability to use B-12 in the methylation cycle (which helps produce energy for our bodies, as well as other critical systems), due to low levels of the enzymes necessary for this process.
Folks that are homozygous (two of these genetic defects) are the ones that have heart attacks at age 40 - likely because their homocysteine is very high. Anyone with low B12 should watch that closely. As far as testing for the defect, my doctor warned against it for my kids due to potential future insurance issues. And, since taking B12 can help with the problem, you can just do that as a preventative - there no issue with toxicity of B12 - you'll pee out the excess.
So, folks like us MUST take additional B12, however, it is highly unlikely that we can absorb it in the gut. Thus, sublingual can be a good choice (either liquid or tablet) for some, but for those of us that have likely been deficient for decades, we need a whole lot more. B12 shots work for some (I don't like those due to high cost and aluminum as a preservative). So, I make up a transdermal B12 solution (doctor approved) - I mix 10,000 mcg of B12 (I just empty the capsules) and 4000 mcg of Folate (folate is very important here as well and a red flag that you have this issue is abnormally high levels of folate in your blood) along with DMSO (20 ml) and 10 ml of distilled water. I save the brown bottles with glass droppers from the herbal tinctures that I use regularly. You could ask a pharmacist if you can buy such. I then apply a dropperful to my inner arm and it gets absorbed. DMSO is used for horses (primarily) to treat muscle aches (pain and inflammation) as it is readily absorbed through the skin (DMSO is di-methyl sulfur oxide). I need to do this everyday periodically and then at least weekly or my levels will drop dramatically. And, I do take a very large dosage sublingual tablet daily and I will take the sublingual liquid when my energy drops. Also, if you take extra B12, you really should take the activated forms of all the B vitamins - they are very synergistic. And, most of us deficient in B12 are deficient in all B vitamins, but few doctors measure those.
The use of DMSO is controversial:
http://www.dmso.org/articles/information/muir.htm
but again, my doctor is totally cool with my usage (she even asked for my recipe). IMHO, the concerns are likely due to big Pharma and the fact that B12 shots are very expensive - as well there are pills that have B12/folate combo (those aren't cheap either). My recipe costs $5.00 per month - you would likely pay that much in one month.
Also, this is such a very, very small amount of DMSO that the potential for ANY side effects is miniscule. I have done this for 5+ years and had only positive results. The big caution is that you can't make big batches - the B12 breaks down in the solution over time. But, a bottle typically lasts me 3 weeks or so. This is also so critical to me that I even take a smaller bottle when I travel (appropriately labeled).
Note, also for your son, there's lots of autistic MDs that use a very aggressive B12 protocol with very positive results - B12 is crucial for the nervous system (as well as well as many other critical processes - again based on the methylation cycle). Here's one good one:
http://www.autism.com/ari/editorials/ed_b12.htm
One thing I have learned in all my research over the past 5 years is that our children's health issues are also very tightly coupled to our own - they are subject to a mother's environment for 9 mos and then they live in a similar environment usually at least for the 1st quarter of their lives. Also, kids are born with a store of B12 and that usually is depleted by age 7. That's when my health issues started as a child and my kids health both went further downhill thereafter. So, they both get lots of B vitamins daily (again the active forms/co-enzymated are better).
