Settle the dose and schedule before the form. Dose is what the sources we read cover, and none of them compares cyanocobalamin with methylcobalamin. The FAO caps the main absorption route at 1.5 to 2.0 micrograms per meal, with 1 to 3 percent of any oral dose getting in by passive diffusion. Everything below hangs on that ceiling.
Why the dose is stranger than it looks
The FAO’s chapter on vitamin B12 describes two routes into the body from a dose you swallow, and the first, through intrinsic factor, is limited to 1.5 to 2.0 micrograms per meal because the receptors that take it up have limited capacity. The second is passive diffusion, which the same chapter puts at between 1 and 3 percent of any particular oral dose.
Those two figures change how a number on a supplement label reads. A label gives you what is in the tablet. The FAO figures describe how much of it the body takes up, and the two are a long way apart once the tablet gets large.
There are two things the chapter we read does not give. It states the cap per meal and says nothing about how soon the receptors are ready to take more, so this article does not stretch the per-meal figure into a daily one. It also describes absorption in general. Nothing in the passage is specific to vegans, to older readers or to anyone with a medical condition, and we are not going to make it specific on its behalf.
How much: the patterns the Vegan Society gives
The Vegan Society sets out three ways to cover B12 and asks vegans to pick one: eat fortified foods two or three times a day for at least 3 micrograms a day, take a daily supplement of at least 10 micrograms, or take a weekly supplement of at least 2,000 micrograms.
Each of those is worded as “at least”. They are floors. The page does not frame any of them as a target to aim at precisely.
Put next to the absorption figures, the patterns make sense to us as arithmetic, though neither organisation draws the link in the passages we read, and the reading here is ours. The Vegan Society’s fortified-food route asks for at least 3 micrograms spread over two or three servings, and a single meal could not take in 3 micrograms through intrinsic factor alone if the FAO’s cap of 1.5 to 2.0 micrograms holds.
The weekly figure of 2,000 micrograms is the one that looks strangest on a label. The Vegan Society passage gives it without the reasoning behind it, and we are not going to supply a reason on its behalf.
Which pattern suits you is mostly a question of habit. A weekly tablet is one thing to remember instead of seven. A daily one keeps each dose small. The fortified-food route only works if you read the B12 figure on every carton and box you rely on, because the 3 micrograms has to come from what you actually eat rather than what the brand range offers.
If you are pregnant or choosing for a child, set the pattern and the dose with a doctor or a registered dietitian rather than from this page. If you are unsure where your levels stand now, ask for a blood test.
Cyanocobalamin or methylcobalamin: where our sources stop
Nothing we read for this article compares the two forms. The Vegan Society passage gives its doses without naming a form, and the FAO passage describes absorption without separating one form from the other. The figures in the last two sections are therefore about B12 in general. They are not evidence either way on which form to buy.
The names describe the group attached to the cobalt at the centre of the molecule, cyanide in one and methyl in the other. The word cyanide in a supplement name is the obvious worry. We were handed nothing that measures it, so this page makes no claim about it in either direction, reassuring or alarming.
This gap is what the rest of the argument is about, and it is worth being plain about it. A page that tells you confidently which form is better, without showing you the comparison, is telling you its preference.
The case each side makes
People who choose methylcobalamin make their case about what the body does with B12 after it gets in: which form the body puts to work, and how many steps stand between the tablet and that form. People who defend cyanocobalamin make theirs about which form the dosing advice was built on, and how the form holds up in a tablet.
The methylcobalamin case is a fair argument in shape. It is about mechanism rather than marketing, and it is easy to see why it appeals. It deserves a reply better than an eye-roll.
Neither side’s claims are carried by anything we read for this article, which is why both are described here as what each side argues and not stated as fact.
Our line, and it is the site’s line rather than a finding, is this. The methylcobalamin argument is about what the body does with B12 once it has it. The only figures this article has are about how much gets in, and those are the figures the Vegan Society’s doses are written around. We would therefore choose on the micrograms and the schedule first, and treat form as the question our sources leave open.
What we’d do, and the part we’re least sure about
Turn the bottle around before you judge it by its name. Find the micrograms per tablet and how often the label tells you to take it, then check that pair against the Vegan Society figures above. A tablet whose name you like and whose numbers fall short of all of them is the wrong tablet, whatever form it is in.
If you already take methylcobalamin, run the same check on it. If you are buying for the first time and the form is the only thing holding you back, let the label’s dose and schedule make the decision, and come back to form when you have something better than a name to judge it on.
The part of this position we are least sure about is the transfer. The Vegan Society’s numbers are written for B12 with no form attached, and nothing we read tells us whether 10 micrograms of methylcobalamin and 10 micrograms of cyanocobalamin should be treated as the same dose. If you have read a comparison of the two at the doses the Vegan Society gives, that is the page we want to read next.
