What two types of B12 are there?

November 16, 2025 •

3 min read

According to one study, up to 90% of vegans are deficient in B12, making supplementation critical for many people. When shopping for a supplement, you will find that there are typically two main forms of B12 available: methylcobalamin and cyanocobalamin.

Quick Summary

This guide explains the primary two forms of vitamin B12 found in supplements: methylcobalamin and cyanocobalamin. It details their key differences, including how they are sourced and processed by the body, to help you make an informed choice.

Key Points

Two Forms: The two most common types of B12 are methylcobalamin, a natural and active form, and cyanocobalamin, a synthetic and stable form.
Methylcobalamin's Advantage: As the active coenzyme form, methylcobalamin is readily usable by the body without conversion and offers higher tissue retention.
Cyanocobalamin's Strength: Cyanocobalamin is widely used in supplements and fortified foods because it is more stable, cost-effective, and effectively converted by most people.
Cost vs. Bioavailability: The choice often involves balancing the lower cost and higher stability of cyanocobalamin against the potentially higher bioavailability and direct activity of the more expensive methylcobalamin.
Individual Needs Vary: The best form depends on individual factors like genetics, absorption efficiency, and specific health goals, making professional medical advice valuable.
No Major Safety Concerns: Both forms are generally safe at recommended doses, with the trace cyanide in cyanocobalamin posing no health risk to healthy individuals.

Methylcobalamin: The Natural and Active Form

Methylcobalamin is one of the two naturally occurring, active coenzyme forms of vitamin B12 in the human body, the other being adenosylcobalamin. It contains a methyl group and is the same form found in animal-derived food sources such as meat, fish, eggs, and dairy. Because it is already in an active form, the body can use it immediately without needing to perform a conversion.

Methylcobalamin plays a crucial role in vital biological processes, most notably in the methylation cycle, where it helps convert the amino acid homocysteine into methionine. This process is essential for cardiovascular health, DNA synthesis, and the production of neurotransmitters. It is also known for its supportive role in nerve health, which is why it is sometimes preferred for those with neurological conditions or issues with nerve damage. While more expensive than its synthetic counterpart, its direct usability and higher tissue retention are major advantages for some individuals.

Potential Benefits of Methylcobalamin

Superior Bioavailability: The body can utilize it directly, requiring fewer metabolic steps.
Higher Retention: Studies suggest it is retained in body tissues for longer, leading to better storage of B12.
Supports Nerve Health: Due to its active role, it is often recommended for individuals with neurological issues.
Sleep Regulation: Research indicates it can help regulate circadian rhythms and improve sleep quality.

Cyanocobalamin: The Synthetic and Stable Form

Cyanocobalamin is a synthetic form of vitamin B12, meaning it is not found naturally in significant amounts in foods. It is the most common form used in dietary supplements and fortified foods due to its low cost and high stability. It contains a cyanide molecule, which is removed and eliminated by the body during conversion. Although this may sound alarming, the amount of cyanide is minimal and not considered harmful for healthy individuals.

Once ingested, cyanocobalamin must undergo several biochemical processes to be converted into the active forms of B12 that the body can use, such as methylcobalamin and adenosylcobalamin. This conversion process is efficient for most people, allowing cyanocobalamin to effectively prevent and treat B12 deficiency.

Advantages of Cyanocobalamin

High Stability: It is more stable and has a longer shelf life compared to methylcobalamin, especially when exposed to light or heat during manufacturing.
Cost-Effective: The manufacturing process is less expensive, making supplements more affordable and widely accessible.
Well-Studied: It has been used for decades and is supported by extensive research on its effectiveness in treating B12 deficiencies, including pernicious anemia.

Comparison: Methylcobalamin vs. Cyanocobalamin

Choosing between these two forms often depends on individual needs, health status, and budget. For those with compromised absorption or certain genetic variations, methylcobalamin's direct bioavailability may be preferable. For the general population, cyanocobalamin remains a stable, affordable, and effective option.


Feature	Methylcobalamin	Cyanocobalamin
Source	Natural; found in animal foods and some supplements.	Synthetic; manufactured for supplements and fortified foods.
Activation	Active form; immediately utilized by the body.	Inactive form; must be converted by the body.
Absorption Rate	Variable; one study suggested slightly lower absorption from a single microgram dose, but higher tissue retention.	Variable; one study showed slightly higher absorption from a single microgram dose, but lower tissue retention and more rapid excretion.
Retention in Tissues	Higher; tends to be retained better in body tissues.	Lower; excreted more rapidly through urine.
Cost	Generally more expensive to manufacture and purchase.	More cost-effective and widely available.
Stability	Less stable; susceptible to degradation from light.	Highly stable; resistant to degradation from light and heat.

Conclusion: Which Type Should You Choose?

Ultimately, both methylcobalamin and cyanocobalamin are effective at raising vitamin B12 levels and preventing deficiency. The decision of which to take is a personal one, best made in consultation with a healthcare professional, especially if you have an underlying health condition or genetic factors that affect B12 metabolism. While cost and stability favor cyanocobalamin, the potential for higher tissue retention and immediate use may make methylcobalamin more appealing for some, particularly those with methylation issues or seeking higher bioavailability. The key takeaway is that both forms can be excellent for addressing nutritional gaps, so long as the dosage and frequency are appropriate for your individual needs.

For a deeper dive into the metabolic pathways of vitamin B12, you can refer to the comprehensive review in Integrated Medicine: A Clinician's Journal focusing on bioavailability and utilization of different forms.

Frequently Asked Questions

The primary difference is their source and biological activity. Methylcobalamin is a natural, active form of B12 that the body can use immediately. Cyanocobalamin is a synthetic, inactive form that the body must convert before it can be utilized.

There is no single 'best' form for everyone, as both effectively treat deficiency. The choice depends on your individual needs, including absorption efficiency, genetics, health goals, and budget. Some people, particularly those with certain metabolic issues, may prefer methylcobalamin.

Yes, cyanocobalamin is considered safe for most healthy people. While it contains a small amount of a cyanide molecule, the body easily detoxifies and excretes it, and the amount is not considered to be a health risk.

Cyanocobalamin is the most common form because it is very stable and inexpensive to produce. This makes it an ideal, cost-effective choice for many supplements and fortified foods.

Research on bioavailability is mixed, but many suggest that because methylcobalamin is the active form, it is more readily available for cellular use and retained in tissues longer. Cyanocobalamin may absorb slightly better initially but is excreted faster.

No, it is not necessary to take both. When cyanocobalamin is processed by the body, it is converted into both of the active coenzyme forms, including methylcobalamin and adenosylcobalamin. A combination supplement may be an option, but either form is effective alone.

Vegans and vegetarians must supplement B12 as it is only naturally found in animal products. Both methylcobalamin and cyanocobalamin are suitable options, with studies suggesting that while methylcobalamin may be naturally derived, cyanocobalamin can also be effective at maintaining B12 levels.