Methylcobalamin & Adenosylcobalamin: Consolidated

It’s raining B12!

I have consolidated all the information from my blog and regarding the benefits and drawbacks of supplementing with the co-enzyme forms, methylcobalamin and adenosylcobalamin, over cyanocobalamin.

Click here: Methylcobalamin & Adenosylcobalamin


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12 Responses to “Methylcobalamin & Adenosylcobalamin: Consolidated”

  1. Tom Walsh Says:

    Hi Jack, I’ve just seen this article and wondered if I should be taking a Glutathione supplement along with B12 (Cyanocobalamin).

  2. Jack Norris RD Says:


    > wondered if I should be taking a Glutathione supplement along with B12 (Cyanocobalamin).

    No need to take a glutathione supplement along with cyanocobalamin.

  3. Dima Says:

    Hi Jack,

    I’ve been looking through scientific literature to figure out how often veg*ns should do cyanocobalamin injections and what dosage should be used. So I needed to know what percentage of the vitamin administered intramuscularly gets absorbed and how long it stays in the body.

    What I have found is quite controversial.

    “The bioavailability of the cobalamin injection is assumed to be 100%”

    “adequate maintenance treatment of uncomplicated vitamin-B12 deficiency states will be achieved by parenteral administration of 1000 mcg cyanocobalamin every 2 months”

    “about 20 per cent CN-B12 being retained after the injection of approx. 1 mg”

    half-life: 6 days in serum, 400 days in liver

    Can you shed some light?

    Also it would be great to see IV B12 recommendations on

    Best wishes.

  4. Jack Norris RD Says:

    Hi Dima–

    I know very little about IV B12 and I don’t really consider it a vegan issue. I would recommend people discuss this with their health professional.

  5. Dima Says:

    Thank you, Jack! I made a typo. I didn’t mean intravenous administration. My question is about intramuscular one, the cheapest and most convenient way to get the vitamin.

  6. Jack Norris RD Says:

    Hi Dima–

    I understood you as meaning as injections rather than oral, so it doesn’t change my views on it which is that I don’t have the inclination to get involved in researching and making recommendations for it.

  7. Dan Says:

    Hi Jack,

    I came across a website which mentions an issue with certain people having issues absorbing cyanocobalamin. I don’t know how factually correct this is but wanted to put the information out there and give you the opportunity to comment on it.

    There are several version of B12 available and the cheapest and most often found in dietary supplements is the cyanocobalamin version, while higher-end supplements uses Methylcobalamin.
    Methylcobalamin is the version found in the blood, though the body is able to convert any of the others such as hydroxocobalamin into this form.

    Research published in the journal “BLOOD”, found that cyanocobalamin may lead to further deficiency in B12 and can be cytotoxic.

    In addition, smokers cannot utilize the B12 molecule in cyanocobalamin because of increased cyanide levels in their blood – due to smoking – reinforcing the cyanide-cobalamin bond, preventing the body from breaking down cyanocobalamin and making use of the cobalamin molecule

    All the best,

  8. Jack Norris RD Says:


    I caution smokers from relying on cyanocobalamin, but anecdotally I haven’t come across any vegan smokers who’ve developed B12 deficiency and I suspect most of them don’t bother taking methylcobalamin rather than cyanocobalamin. People with cyanide metabolism defects that cause an accumulation of cyanide in the body should stay away from cyanocobalamin.

  9. Dima Says:

    This is the study mentioned by Dan

  10. Jack Norris RD Says:


    Thanks for the link. I don’t have the expertise to assess that study other than to say that how things work in vitro doesn’t always follow the same pattern in the human body. It would be great if there were clinical trials of vegan smokers taking cyanocobalamin vs. vegan smoker controls to see how effective it is, but short of that, as I said previously, I’m not aware of cyanocobalamin being a problem for vegan smokers. If I was a smoker, I’d probably get my MMA levels tested every few years to make sure the cyanocobalamin was working.

  11. Russell Long Says:


    This was a bit of a shocker on the Vitamin B issue in the news today:

    Any thoughts on it?



  12. Jack Norris RD Says:

    I’ll get a copy and check it out.

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