Methylcobalamin vs Hydroxocobalamin: Which B12 Form to Choose

Methylcobalamin and hydroxocobalamin are both natural forms of vitamin B12. Methylcobalamin is one of the two active forms your body uses directly, while hydroxocobalamin, used in prescription injections, becomes active after the body converts it. For everyday B12 support without a prescription, methylcobalamin is the ready to use form; here is how the two compare, and where cyanocobalamin fits.

Key Takeaways

• Methylcobalamin is one of the two active forms of vitamin B12; hydroxocobalamin and cyanocobalamin become active after the body converts them (NIH Office of Dietary Supplements, 2024).
• Methylcobalamin works with folate in red blood cell formation, while adenosylcobalamin, the other active form, supports the metabolism of fats, carbohydrates and amino acids and the formation of myelin (Thakkar and Billa, 2015).
• A 2017 review of human studies reported lower tissue retention with cyanocobalamin than with methylcobalamin, hydroxocobalamin or adenosylcobalamin, and recommended the natural forms (Paul and Brady, 2017).
• Hydroxocobalamin is used in prescription injections, and in small studies a hydroxocobalamin nasal spray raised blood B12 in adults, older adults and children (Slot et al., 1997).
• Adults need 2.4 mcg of B12 a day, and no upper limit has been set because B12 has a low potential for toxicity (NIH Office of Dietary Supplements, 2024).

What Are Methylcobalamin and Hydroxocobalamin?

Vitamin B12 is a family of related molecules called cobalamins. They share the same core, built around a cobalt atom, and differ in the small group attached to it. That group gives each form its name: a methyl group in methylcobalamin, a hydroxyl group in hydroxocobalamin, a cyanide group in cyanocobalamin and an adenosyl group in adenosylcobalamin.

Your body runs on two of these. Methylcobalamin and adenosylcobalamin are the metabolically active forms, and hydroxocobalamin and cyanocobalamin become active after they are converted. Cyanocobalamin is the most common form in supplements, and methylcobalamin, adenosylcobalamin and hydroxocobalamin are also sold (NIH Office of Dietary Supplements, 2024). For a closer look at the methyl form, see our Methyl B12 (methylcobalamin) ingredient page.

Hydroxocobalamin vs Cyanocobalamin vs Methylcobalamin

Here is how the three forms people compare most often line up:

Question	Methylcobalamin	Hydroxocobalamin	Cyanocobalamin
Natural form?	Yes	Yes	No, a form used mainly in supplements
Active as it is?	Yes, one of the two active forms	Becomes active after conversion	Becomes active after conversion
Tissue retention in human studies	Higher than cyanocobalamin	Higher than cyanocobalamin	Lowest of the forms reviewed
Where you usually find it	Capsules, sublingual tablets and nasal sprays	Prescription injections, some supplements	Most supplements
Need a prescription?	No	For injections, yes	For injections, yes

The tissue retention row comes from a 2017 review that drew on earlier human studies and reported lower retention of B12 after cyanocobalamin than after the natural forms, which the authors linked to less efficient uptake and activation in cells (Paul and Brady, 2017). For the full head to head on the most common pair, see methylcobalamin vs cyanocobalamin.

How Your Body Uses Each Form

The two active forms do different jobs. Methylcobalamin works with folate in forming red blood cells and in brain development during childhood. Adenosylcobalamin supports the metabolism of carbohydrates, fats and amino acids and the formation of myelin, the coating around nerves (Thakkar and Billa, 2015). Methylcobalamin is the form used by methionine synthase, an enzyme in the methylation cycle, and it is made in the main fluid of the cell, while adenosylcobalamin is made inside the mitochondria (Paul and Brady, 2017).

Hydroxocobalamin has to be converted before it can do either job. That does not make it a poor form. It is natural, it is well retained, and it is one of the forms used for injections. Methylcobalamin simply arrives as one of the working forms. These roles are why B12 matters for everyday energy, nerves and red blood cells; our guide to vitamin B12 benefits covers them in more depth, and our hub on cellular energy and mitochondrial health shows where B12 fits in the bigger picture.

Injections, Nasal Sprays and Oral Forms

Injections

B12 can be given as a prescription medicine, usually by injection into the muscle (NIH Office of Dietary Supplements, 2024). Hydroxocobalamin is one of the forms given this way (Paul and Brady, 2017). The schedule is set by the prescribing clinician.

Nasal sprays

Several small studies have tested hydroxocobalamin as a nasal spray. In 6 adults with low blood B12 (below 200 ng/L), 1,500 mcg sprayed into the nose on days 0, 14 and 21 raised blood B12, and starting levels stayed higher through the 5 week study, with no side effects noted (Slot et al., 1997). In 10 healthy adults with an average age of about 72, single nasal doses of 750 and 1,500 mcg raised blood B12 and caused no signs of nasal irritation (van Asselt et al., 1998). In 10 children with low B12, a hydroxocobalamin nasal spray raised average blood B12 from about 126 to about 1,915 pmol/L, with no side effects reported (Estourgie-van Burk et al., 2020).

Our Methyl B-12 Nasal Spray uses the active methylcobalamin form: 408 mcg of vitamin B12 as methylcobalamin in every 2 spray serving, with alkaline water as the only other ingredient, used once a day. It is absorbed through the lining of the nose instead of being swallowed like a capsule, so some of each dose skips digestion. Our guide to B12 nasal spray vs injections compares the two routes side by side.

Oral and sublingual forms

B12 you swallow is absorbed mainly with the help of intrinsic factor, a protein made in the stomach (NIH Office of Dietary Supplements, 2024). Capsules and tablets usually contain cyanocobalamin or methylcobalamin. Tablets that dissolve under the tongue are another option; see sublingual B12 for how they compare.

Methylcobalamin or Hydroxocobalamin: Which Should You Choose?

• If a clinician has prescribed injections, follow that plan. The choice of injected form and schedule is theirs to make.
• For everyday B12 support without a prescription, methylcobalamin is the natural, ready to use active form, and it comes as capsules, sublingual tablets and nasal sprays.
• If you prefer not to swallow pills, a methylcobalamin nasal spray or a sublingual tablet avoids capsules altogether.
• Read the label. Look for the form named in brackets, for example "vitamin B12 (as methylcobalamin)", and the amount in mcg per serving.
• Count every source. B12 also comes from fish, meat, eggs and dairy; our guide to vitamin B12 foods lists the richest ones.

Safety and Who Should Check First

B12 has a low potential for toxicity, and no upper intake limit has been set for it (NIH Office of Dietary Supplements, 2024). Our guide can you take too much B12? explains what high blood levels on a lab report can mean. A few cautions still apply:

• Medicines. Talk to your doctor if you take metformin or acid reducing medicines such as proton pump inhibitors (omeprazole) or H2 blockers (cimetidine), because they can lower B12 absorption from food.
• Absorption problems. If you have been told you have pernicious anemia or have had stomach or bowel surgery, work with your clinician on a plan rather than choosing a form on your own.
• Pregnancy and breastfeeding. Needs rise to 2.6 mcg a day in pregnancy and 2.8 mcg while breastfeeding; check with your provider before starting a new product.
• Nasal sprays. Brief nasal irritation or a runny nose is the most common complaint with nasal sprays. Stop using a spray if you have a reaction.
• Injections. Prescription injections, including hydroxocobalamin, are given under a clinician's care; report any reaction to the prescriber.

If you also take an NAD+ precursor, our Enhanced NMN includes vitamin B12 as methylcobalamin, 750 mcg per 2 capsule serving, alongside 750 mg of NMN and 200 mg of TMG, another methyl donor.

Frequently Asked Questions

Is methylcobalamin or hydroxocobalamin better?

Both are natural forms that the body retains better than cyanocobalamin. Methylcobalamin is already one of the two active forms, which makes it a simple choice for everyday B12 support without a prescription. Hydroxocobalamin is converted before use and is one of the forms used for prescription injections. If a clinician has prescribed injections, follow that plan.

What is the difference between hydroxocobalamin and methylcobalamin?

They share the same cobalamin core and differ in the group attached to its cobalt atom: a hydroxyl group in hydroxocobalamin and a methyl group in methylcobalamin. Methylcobalamin is an active form that works with folate in the methylation cycle. Hydroxocobalamin becomes active after the body converts it, and it is one of the forms used in prescription injections.

Hydroxocobalamin vs cyanocobalamin vs methylcobalamin: which should I pick?

For everyday use, many people choose methylcobalamin because it is a natural, active form. Cyanocobalamin is the most common form in supplements and fortified foods, and a 2017 review of human studies found it is retained in tissues less well than the natural forms. Hydroxocobalamin is used in prescription injections, so that choice rests with your clinician.

Does hydroxocobalamin convert to methylcobalamin?

Yes. According to the NIH Office of Dietary Supplements, hydroxocobalamin and cyanocobalamin become biologically active after the body converts them into the active forms, methylcobalamin and adenosylcobalamin. Methylcobalamin is made in the main fluid of the cell, and adenosylcobalamin inside the mitochondria. Taking methylcobalamin supplies one of those active forms directly.

Is hydroxocobalamin only available as an injection?

No. Hydroxocobalamin is used in prescription injections, and it is also sold in some oral products, and researchers have tested it as a nasal spray in adults, older adults and children, where it raised blood B12. For B12 without needles or a prescription, methylcobalamin capsules, sublingual tablets and nasal sprays are widely available.

Which form of B12 is in a nasal spray?

It depends on the product, so check the label. The published nasal studies described above used hydroxocobalamin. Our Methyl B-12 Nasal Spray uses methylcobalamin, the active form: 408 mcg per 2 spray serving, with alkaline water as the only other ingredient, used once a day. It is absorbed through the lining of the nose instead of being swallowed like a capsule.

Can you take methylcobalamin and hydroxocobalamin together?

B12 has a low potential for toxicity, and no upper intake limit has been set for it. If you receive hydroxocobalamin injections, tell your prescriber about any B12 you take at home, because it can raise your blood B12 results, which your prescriber may use to plan your care.

Is it safe to take methylcobalamin every day?

Yes, for most adults. Adults need 2.4 mcg of B12 a day, and no upper limit has been set because B12 has a low potential for toxicity. Talk to your doctor first if you take metformin or acid reducing medicines, or if you are pregnant or breastfeeding. With a nasal spray, brief nasal irritation is the most common complaint.

Sources

• NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. Updated March 26, 2024. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
• Thakkar K, Billa G. Treatment of vitamin B12 deficiency: methylcobalamine? Cyancobalamine? Hydroxocobalamin? Clearing the confusion. European Journal of Clinical Nutrition, 2015. https://pubmed.ncbi.nlm.nih.gov/25117994/
• Paul C, Brady DM. Comparative bioavailability and utilization of particular forms of B12 supplements with potential to mitigate B12-related genetic polymorphisms. Integrative Medicine: A Clinician's Journal, 2017. https://pubmed.ncbi.nlm.nih.gov/28223907/
• Slot WB, Merkus FW, Van Deventer SJ, Tytgat GN. Normalization of plasma vitamin B12 concentration by intranasal hydroxocobalamin in vitamin B12-deficient patients. Gastroenterology, 1997. https://pubmed.ncbi.nlm.nih.gov/9247460/
• van Asselt DZ, Merkus FW, Russel FG, Hoefnagels WH. Nasal absorption of hydroxocobalamin in healthy elderly adults. British Journal of Clinical Pharmacology, 1998. https://pubmed.ncbi.nlm.nih.gov/9489599/
• Estourgie-van Burk GF, van der Kuy PHM, de Meij TG, et al. Intranasal treatment of vitamin B12 deficiency in children. European Journal of Pediatrics, 2020. https://doi.org/10.1007/s00431-019-03519-0

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.