Sarge, the company you are describing is JARROW (not Yarrow).
It is one of the first who offered oral methylcobalamin and at one time was only available on iherb.com

Today we have other suppliers which are at Puritan's Pride, Costco and Walgreens and perhaps other local places. In the old days, over a decade ago we were only able to get it online.

I tested out the Puritan's myself, and at 5mg a day reached a blood level of 1999 (the top of the calibration range).

And as I mentioned before, if the MTHFR mutation is present, then one needs the methylfolate also.

We are rather fortunate that in some ways repairing B12 levels is fairly simple, now, and inexpensive. Information changes, new studies come out, and like most medical things, are not cast in stone. Still doctors may cling to their old therapeutic manuals, which were printed before 2003. The AAFP link I provide gives new medical information targeting doctors, in 2003 and still people cling to the "old ways".

I personally think once a month shots are artificial. We evolved getting our B12
orally from food. When that fails (due to low acid in the stomach or damaged intrinsic factor), then high dose oral is the next best thing IMO. A study I provided earlier shows that 1000mcg oral yields about 13mcg absorbed into the blood.(the remainder is excreted in the stool. This is about 2.5 times the RDA. Injectables only last in the blood for 72 hours, and the excess is excreted, since only minute micrograms can be handled at a time by the systems in the tissues. The same study showed 145mcg in the blood following an injection of 1000mcg. So people getting injections do not all get lasting benefits that way. If you read the whole B12 thread you will find those people who didn't do well on injectable ALONE.