There are different versions of the supplement. Some just raise the vitamin in the blood. What is the name of the substance that is working best? Much appreciated.

The one you want is methylcobalamin, it becomes B12 immediately and has better absorbtion, and this article says that it has a big effect on accumulated mercury, cyanocobalamin is the type that is sold most commonly but it doesn't even occur in nature according to Wiki.

[en.wikipedia.org]
Cyanocobalamin usually does not even occur in nature, and cyanocobalamin is not one of the forms of this vitamin which is directly used in the human body (or that of any other animal). However, animals and humans can convert it to active (cofactor) forms of the vitamin, such as methylcobalamin.

[www.howweheal.com]
12) Inorganic mercury is known to accumulate on the BBB. It is thought that it oxidises the cobalt atom in methylcobalamin, making it far less able to cross the barrier. Inorganic mercury is thus a creator of deficiency of B12 in the nervous system and symptoms usually attributed to mercury toxicity in the brain and nerves are due to its effect on B12. Inorganic mercury exposure is most commonly from mercury amalgam dental fillings and vaccines. Psychiatrist John Dommisse in the USA claims to have reversed 100% of his pre-Alzhemiers patients with the use of methylcobalamin as well as many cases of depression. Methylcobalamin is highly recommended by the Swedish Association of Dental Mercury Patients. It has been used successfully in the treatment of Chronic Fatigue Syndrome and Fibromyalgia - more than 60% of these patients have tested for low levels in the cerebrospinal fluid. It has been used successfully as part of treatments in Autism, Schizophrenia and Multiple Sclerosis and has great potential in Parkinson's Disease and Muscular Dystrophy as well as other neurological or psychological disorders. In such cases intramuscular injections or sublingual liquids or lozenges of methylcobalamin are maximally effective in combating deficiency symptoms since they by-pass the complex absorption process in the intestines. There is no evidence for toxicity of methylcobalamin. Up to 40mg per day has been used therapeutically in some cases. Large doses have been used since it must overwhelm the effect of any mercury on the BBB.

Great info everyone! Thank you!(and I didn't even start this thread! lol)

Thanks!