Serum B12
Test First
Sources of Information

The best available tests for B12 deficiency are the metabolites, methylmalonic acid and total homocysteine.

It is essential that, for diagnosis of B12 deficiency, you do not take any form of B12 supplements or injections before having these metabolite tests.

By failing to test first, the the patient faces this dilemma:

1. No metabolite tests, no treatment, with B12 deficiency:

  • Increasing disability
  • Eventual irreversible damage or death likely
2. No metabolite tests, taking supplements or having injections, no B12 deficiency:
  • Unnecessarily taking supplements, or having injections, for life
  • Risk of masking folate deficiency

I suggest that anyone with suspected vitamin B12 deficiency to test thoroughly first, then, if necessary, urgently commence treatment. If you take any treatment for vitamin B12 deficiency first then you risk masking other causes of symptoms, especially folate deficiency; you also lose the opportunity to use the best available tests.

If you either take B12 supplements, or have B12 injections, before proper diagnosis then you do not know whether or not you actually have a vitamin B12 deficiency. This is because the tests recommended by experts, methylmalonic acid and homocysteine, are used by comparing levels before and after treatment.

Once you have commenced treatment, it is not possible to return to your pre-treatment condition to obtain the "before" result.

The problem is that, unlike most other vitamins, vitamin B12 is normally stored for a very long time in your body, the majority of it in your liver. In a healthy person, your body supply of B12 is almost entirely recycled. The stored B12 is excreted in the bile, into your intestine, where it is re-absorbed; this is called entero-hepatic recycling. According to some experts, your body store is sufficient to last for 20 years. You can read about this in detail in the article by Victor Herbert, my reference EA08. So, if a healthy person suddenly stops taking any B12 in their diet, by becoming a vegan, it can take decades for the B12 deficiency to develop.

If anything interferes with the recycling of your body store of B12, the store will eventually deplete and you will develop a cellular B12 deficiency.

If you develop a problem with B12 intake or recycling, for any reason, the time it takes to deplete your body stores will depend on the severity of the problem. For example, some experts quote a figure of 1 to 3 years before your stores become depleted, if you develop pernicious anaemia, where there is no recycling.

If your stores are depleted, and you commence taking supplements or have B12 injections, you will immediately start to fill your body stores. Even if you cannot absorb much or any B12 normally, for example because of atrophic gastritis or PA, you can still absorb some. This is possible because of a process called "passive diffusion", which will allow you to absorb about 1% of any dose. About 200 to 300 doses, of 1000 µg each, will be sufficient to reach the 2 to 3 mg required. If you do not have total malabsorption, or if you take higher doses, your store will fill more quickly.

So, what happens if you suspect that you have a B12 deficiency and start treatment? If your body store of B12 was not depleted, the additional intake is excreted, so it makes no difference. If your store was depleted, you will add some B12 to it, increasing the amount of active B12 (holotranscobalamin) available to the cells. If your cells are able to utilize the additional B12, this will cause the level of your methylmalonic acid and homocysteine to fall.

You then do not have a valid “before” result to compare with the “after” treatment result. If you now test for MMA and homocysteine, your results should be normal. This does not tell you what your results would have been before treatment, and that is what is really important.

My own research shows that it can take a very long time, after ceasing treatment, for your serum B12 vitamin level to fall to a level suggesting a deficiency. This is very dangerous because neurological damage, caused by cellular deficiency, can occur even at high serum vitamin B12 levels and with normal haematology. This is why it is so important to get the evidence of disease before taking the supplement or having the injections.

Once you have interfered with the body store of B12, by taking treatment, you cannot go back to the pre-treatment condition. You have no way of knowing how depleted the body store was, and no safe way to deplete it again.

It is not possible to simply monitor your serum B12 level in the hope of observing the onset of deficiency. You can develop irreversible neurological damage from B12 deficiency, even when your B12 levels do not fall to abnormally low levels.

After ceasing supplements, the serum B12 level is not useful in detecting the developing cellular deficiency.

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