vitamin B12
noun
1
: a complex cobalt-containing compound C63H88CoN14O14P that occurs especially in liver, is essential to normal blood formation, neural function, and growth, and is used especially in treating pernicious and related anemias and in animal feed as a growth factor
called also cyanocobalamin
2
: any of several compounds similar to vitamin B12 in action but having different chemistry
Examples of vitamin B12 in a Sentence
Recent Examples on the Web
That said, there’s no scientific evidence that taking a vitamin B12 supplement, or even eating more foods with vitamin B12, can stop hair loss from happening.
—
Rebecca Strong, USA Today, 16 Feb. 2026
Each drink has 2 billion probiotics and vitamin B12 for energy.
—Bestreviews, Chicago Tribune, 16 Feb. 2026
Mayo Clinic says metformin is generally safe, but can cause digestive side effects and vitamin B12 deficiency in some patients.
—Khloe Quill, FOXNews.com, 10 Feb. 2026
And a vitamin B12 deficiency can lead to high levels of homocysteine, Dr. Klodas points out.
—Mara Santilli, Flow Space, 5 Feb. 2026
Sardines have about 10 times more vitamin B12 than anchovies.
—Mark Gurarie, Health, 3 Feb. 2026
Both magnesium and vitamin B12 supplements are most helpful when used to correct deficiencies and under the guidance of a healthcare provider.
—Kristen Gasnick, Verywell Health, 27 Jan. 2026
Additionally, mackerel is an excellent source of omega-3 fatty acids, along with selenium, vitamin B12, and vitamin D, says Lorenz.
—Kirsten Nunez, Martha Stewart, 27 Jan. 2026
Some insist the drug must be paired with vitamin B12, omega-3, or a certain amino acid; others caution that dairy can reduce its effectiveness.
—Tom Bartlett, The Atlantic, 19 Dec. 2025
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Rebecca Strong, USA Today, 16 Feb. 2026
Each drink has 2 billion probiotics and vitamin B12 for energy.
—Bestreviews, Chicago Tribune, 16 Feb. 2026
Mayo Clinic says metformin is generally safe, but can cause digestive side effects and vitamin B12 deficiency in some patients.
—Khloe Quill, FOXNews.com, 10 Feb. 2026
And a vitamin B12 deficiency can lead to high levels of homocysteine, Dr. Klodas points out.
—Mara Santilli, Flow Space, 5 Feb. 2026
Sardines have about 10 times more vitamin B12 than anchovies.
—Mark Gurarie, Health, 3 Feb. 2026
Both magnesium and vitamin B12 supplements are most helpful when used to correct deficiencies and under the guidance of a healthcare provider.
—Kristen Gasnick, Verywell Health, 27 Jan. 2026
Additionally, mackerel is an excellent source of omega-3 fatty acids, along with selenium, vitamin B12, and vitamin D, says Lorenz.
—Kirsten Nunez, Martha Stewart, 27 Jan. 2026
Some insist the drug must be paired with vitamin B12, omega-3, or a certain amino acid; others caution that dairy can reduce its effectiveness.
—Tom Bartlett, The Atlantic, 19 Dec. 2025
Cite this Entry
“Vitamin B12.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/vitamin%20B12. Accessed 23 Feb. 2026.
Copy CitationMedical Definition
vitamin B12
noun1
: a complex cobalt-containing compound C63H88CoN14O14P found in animal products (as meat and eggs) that is essential to normal blood formation, neural function, and growth and is used especially in treating pernicious and related anemias and in animal feed as a growth factor
called also cyanocobalamin
2
: any of several compounds similar to vitamin B12 in action but having different chemistry
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