Thanks, mrsD and pabb. This is the only exclusively B12 supplement (mecobalamin) available at my local chemist (note that I'm not in the US). They come in 500mcg tabs:

http://www.eisai.jp/medical/products...L_T-FG_EPI.pdf

Other formulations come as B1-B6-B12 combinations and the B12 component is cyanocobalamin which I believe is not as effective as mecobalamin?

What would be the normal range for B12 count using the North American system of measurement? We use pg/ml here. I thought this was the same as in the US?