I have a problem with taking B12, they make me feel irritable. This is, it seems, a problem for others too. I have just ordered some Vitamin B12 tablets - Sublingual Methylcobalamin from Cytoplan.co.uk. These are not available from Holland and Barrett. I haven't got them yet but will let this forum know how I get on with them. They dissolve under the tongue, might make a difference as they do not go into the stomach, or something like that. Apparently the Methyl bit is important (I think it refers to folic acid). Cytoplan seem to have a wide range of vitamins and minerals so worth a look.