There is a patent on making methyl B12.... so I would suspect
most of the raw material is from one source (or very few). This is common in the supplement industry. At one time a high % of all our vitamins came originally from Roche... who made them in Europe.
But that has changed, by now I would think.
This link explains how Roche was accused of "price fixing"
http://www.quackwatch.com/02Consumer...rochefine.html
and
http://en.wikipedia.org/wiki/Hoffmann-La_Roche

Kirkland has an excellent quality control, so I don't expect any
problems with it. In fact hubby just called from Costco, as he did find it there this morning. We are just about out of our Puritan's here.

I did test out Puritan's when they began to offer it 2 yrs ago. I tested at 1999 after 3 months. My doctor insisted that oral would not work, and she was stunned at my test results.

Take all methylB12 on an empty stomach. I chew them up and follow with water first thing in the morning.