Once people hear I’ve been plant-based since 2016, the supplement question comes up fast. My answer is always the same: vitamin B12, and nothing else. The follow-up is usually cyanocobalamin vs methylcobalamin. Which form of B12 should you buy? I take cyanocobalamin, the cheap, stable, well-studied form Dr Michael Greger recommends, and in this post I’ll explain why.
I said it in my green smoothie guide and I’ll say it again: if you eat a proper plant-based diet (fruit, vegetables, legumes, whole grains, nuts and seeds), the only supplement you need is B12. That’s still where I stand, and my blood tests have backed it up every time.
Key takeaways
- Plants don’t make B12. Microbes do. Anyone on a vegan or plant-based diet needs a B12 supplement, fortified foods, or both.
- Dr Greger calls cyanocobalamin “the preferred supplemental form of vitamin B12” and says there isn’t enough evidence for other forms like methylcobalamin.
- His dose for adults under 65 is at least 50 mcg a day or 2,000 mcg once a week. Over 65, he suggests at least 1,000 mcg a day.
- Fortified foods can work in Australia, but you need three spaced servings a day. Original Vegemite has no B12 at all.
- Deficiency can take years to show and nerve damage may not fully reverse. Don’t wait for symptoms. Ask your GP about testing.
Why plant-based eaters need a B12 supplement
Vitamin B12 (cobalamin) is an essential nutrient. Your body needs it for red blood cell formation, DNA synthesis and a healthy nervous system. It isn’t made by plants or animals. It’s made by bacteria. Animals build it up in their tissues, which is why meat, eggs and dairy contain some.
Dr Greger’s explanation on NutritionFacts.org stuck with me: we used to get B12 from dirt and untreated water, along with a lot of bugs we’re happy to be rid of. Today’s washed vegetables and chlorinated tap water don’t give you a dose you can count on. I’ll take the tablet.
Your liver stores B12, sometimes for years. That’s the trap. People stop eating animal products, feel fine for a long time, and then they’re not fine. When I went fully plant-based in 2016, I spent about five months reading before I made the switch (I wrote about that in my post on Ven. Soma Thera), and B12 was the one thing every credible source agreed on. Dr Neal Barnard says the same thing in my post on getting enough iron without meat.
Cyanocobalamin vs methylcobalamin: what’s the difference?
Both are forms of vitamin B12. The difference is the small group attached to the cobalt at the centre of the molecule.
Cyanocobalamin is the synthetic form. It carries a cyanide group, which makes it very stable on the shelf. It’s the most common form used in supplements and fortified foods, it’s cheap, and it’s the form most of the research on preventing deficiency has used.
Methylcobalamin carries a methyl group instead. It’s one of the two coenzyme forms your body actually uses (the other is adenosylcobalamin), so it gets marketed as the “natural” or “active form of B12”. It usually costs more and is less stable, especially in light.
What the marketing tends to skip is that your body converts cyanocobalamin into methylcobalamin and adenosylcobalamin anyway. You don’t need to buy the active form to end up with it.
Which form of B12 is best absorbed?
This is where the debate usually goes. A 2017 review by Paul and Brady, “Comparative Bioavailability and Utilization of Particular Forms of B12 Supplements”, found the differences in bioavailability between the two forms are small. Cyanocobalamin may be absorbed slightly better, and methylcobalamin may be retained slightly better. Neither came out as the clear winner for the average healthy adult.
Dr Greger’s position on NutritionFacts is plain: his doses “are specific to cyanocobalamin, the preferred supplemental form of vitamin B12, as there is insufficient evidence to support the efficacy of the other forms, like methylcobalamin.” That’s good enough for me.
Why avoid cyanocobalamin? (You probably don’t need to)
The word “cyanide” scares people. The amount in a B12 tablet is tiny and your body clears it easily. If you have kidney disease, Leber’s hereditary optic neuropathy, or you’re a heavy smoker, talk to your doctor about which form suits you. For everyone else, it’s a non-issue.
Why do doctors prescribe cyanocobalamin?
It’s stable, inexpensive and well studied, and the standard dosing advice is built on it. In Australia, B12 injections are usually hydroxocobalamin, which is a different form again and a medical treatment rather than something you pick up at the chemist.
| Form | What it is | Dr Greger’s view | When I’d use it |
|---|---|---|---|
| Cyanocobalamin | Synthetic, stable, cheap | Preferred form; his doses are written for it | Daily or weekly tablet |
| Methylcobalamin | Coenzyme “active” form, dearer, less stable | Not enough evidence for it | Only if my GP had a reason |
| Hydroxocobalamin | Common injection form in Australia | Medical treatment | If a doctor prescribes injections |
| B12 in a multivitamin | Small dose in a mix | Easy to under-dose | I don’t rely on it |
How much B12 should you take?
These are Dr Greger’s current recommendations from NutritionFacts.org, all for cyanocobalamin:
- Adults under 65: at least 50 mcg a day, or at least 2,000 mcg once a week.
- Adults 65 and over: at least 1,000 mcg a day, because absorption drops with age.
Those numbers look huge next to the 2.4 mcg on a nutrition label. The reason is absorption. Your gut can only take up a small amount of B12 at a time through its normal pathway, and a high dose works because a small percentage gets in passively. That’s why a single 2,000 mcg tablet once a week can cover you.
Pick whichever pattern you won’t forget. Daily works if you already have a morning routine. Weekly works if you tie it to a fixed day. If you’re pregnant, breastfeeding, raising plant-based kids, on metformin, or already low in B12, get a plan from your GP rather than copying mine.
Fortified foods in Australia vs a tablet
Australia only lets manufacturers add B12 to a limited set of foods. The ones you’ll actually find are some fortified soy milks (not every almond or oat milk, so read the panel), some plant-based meat alternatives, fortified nutritional yeast, and Vegemite 40% Less Salt.
That last one surprised me. Original Vegemite has B1, B2, B3 and folate but no B12. Only the 40% Less Salt version is fortified with B6 and B12, at about 0.5 mcg per 5 g serve.
If you’d rather skip tablets, Dr Greger’s food option is three servings a day of fortified foods, each giving at least 2 mcg, eaten four to six hours apart. That’s a lot of label-reading and timing for something a tablet solves. I treat fortified soy milk as a bonus, not the plan.
| Source | Where to get it | What “enough” looks like | My take |
|---|---|---|---|
| Cyanocobalamin tablet | Chemist or supermarket | 50 mcg daily or 2,000 mcg weekly | Most reliable |
| Fortified soy milk | Chilled or long-life carton | Only if B12 is on the panel | Easy extra, easy to miss |
| Nutritional yeast | Fortified flakes | Check the label every time | Brands vary a lot |
| Vegemite 40% Less Salt | Supermarket | About 0.5 mcg per serve | Nice on toast, not a source to rely on |
| Unfortified plants | Vegetables, beans, grains | No B12 | Eat them anyway |
Signs of vitamin B12 deficiency
Dr Greger calls B12 deficiency “the great masquerader” because the symptoms look like so many other things: tiredness, brain fog, pins and needles, poor balance and a type of anaemia (megaloblastic anaemia). In serious cases it causes nerve damage that may not fully reverse. Babies of parents who eat plant-based and don’t supplement can get into trouble much faster than adults.
Some people can’t absorb B12 from food or tablets properly. Pernicious anaemia, an autoimmune condition, is the classic example. Age, some stomach conditions and medications like metformin can lower absorption too. Those cases need a doctor, and often injections.
Waiting until you feel deficient is a bad strategy. Tell your GP you eat plant-based and ask about checking your B12 levels. A standard serum B12 test doesn’t always catch an early problem, so your doctor may also look at markers like homocysteine or methylmalonic acid.
How I take B12
My plant-based journey began in 2016. I went vegetarian overnight to see if it would help my migraines. It didn’t, but I kept going because I had more energy and recovered faster from colds. Then I went fully plant-based.
I take a plain cyanocobalamin supplement. No multivitamin, no cupboard full of anti-ageing pills. The bottle sits next to my blender so it’s part of the smoothie habit. Food does the rest: the Daily Dozen on the plate, greens and berries in the blender, and the habits from the Anti-Aging Eight. My blood results have been good every time, and B12 is the one gap food can’t fill.
If migraines are your other battle, I’ve written about ginger root capsules and foods that fight pain. A new multivitamin won’t fix them.
FAQ
Is cyanocobalamin or methylcobalamin better?
For most healthy adults, cyanocobalamin. It’s stable, cheap and well studied, and Dr Greger’s dosing advice is written for it. Methylcobalamin hasn’t been shown to be better at preventing deficiency.
What is the disadvantage of methylcobalamin?
It usually costs more, it’s less stable, and there’s less evidence behind it for preventing B12 deficiency. It isn’t harmful. If your doctor has put you on it for a reason, stick with their advice.
Do vegans need vitamin B12?
Yes. There’s no reliable plant source of B12, so vegans and anyone eating mostly plants need a supplement, fortified foods, or both.
How much B12 should I take on a plant-based diet?
Dr Greger recommends at least 50 mcg of cyanocobalamin a day or 2,000 mcg once a week for adults under 65, and at least 1,000 mcg a day for those 65 and over. Check with your GP if you’re pregnant, on medication or already low.
Does Vegemite have B12?
Original Vegemite doesn’t. Vegemite 40% Less Salt is fortified with B12, but only about 0.5 mcg per serve, so it won’t cover you on its own.
Should I get my B12 levels tested?
Yes, especially if you eat plant-based, are over 50, are pregnant, or have symptoms. Ask your GP which tests make sense for you.
To your health
Going plant-based is one of the best things I’ve done for my health, and taking B12 is part of doing it properly. Go and check the bottle in your cupboard. If there isn’t one, pick up a plain cyanocobalamin this week. To good health, to your health, and to your prosperity.
This article shares my personal experience and is not medical advice. Please talk to your doctor before changing your diet, supplements or medication.