What's the Difference Between B12 and Folate?

October 15, 2025 •

4 min read

According to the National Institutes of Health, B12 and folate (B9) are both essential B vitamins that play a crucial role in DNA synthesis, red blood cell production, and cell division, but they are distinct in their sources, absorption, and potential deficiency symptoms. Understanding what's the difference between B12 and folate is key to maintaining a healthy diet and preventing health issues like megaloblastic anemia and nervous system damage.

Quick Summary

This article explores the fundamental differences and critical interplay between vitamin B12 and folate. Both are vital for cellular function and red blood cell production, yet they differ significantly in their dietary sources, absorption methods, and consequences of deficiency, particularly regarding neurological health. The piece also details their synergistic relationship and how dietary choices, supplementation, and genetic factors influence their status within the body.

Key Points

Sources differ: B12 comes from animal products, while folate is found in leafy greens and legumes, making vegans and older adults more prone to B12 deficiency.
Absorption is different: B12 requires intrinsic factor for absorption, which can be affected by age and conditions like pernicious anemia, while folate absorption can be affected by genetic factors and some medications.
Deficiency symptoms overlap: Both deficiencies cause megaloblastic anemia symptoms like fatigue and weakness, but only B12 deficiency leads to irreversible neurological damage.
Folic acid can mask B12 deficiency: High doses of supplemental folic acid can correct the anemia from a B12 deficiency without resolving the underlying neurological damage, masking a serious problem.
B12 and folate work together: These two vitamins are interdependent for one-carbon metabolism, with B12 activating folate to ensure proper functioning in cellular processes.
High-risk groups exist: Older adults, vegans, pregnant women, and individuals with certain gastrointestinal disorders are most at risk and should monitor their intake.
Consult a professional: Given the complex relationship and masking potential, it's crucial to consult a healthcare provider before starting high-dose supplementation.

B12 and Folate: The Dynamic Duo of Cellular Health

While often mentioned together due to their collaborative roles in the body's metabolic processes, vitamin B12 (cobalamin) and folate (vitamin B9) are not interchangeable. Their intricate working relationship is central to several vital functions, including the production of red blood cells, the synthesis of DNA and RNA, and the metabolism of amino acids. A deficiency in either can lead to similar issues, such as megaloblastic anemia, but a closer look reveals key distinctions in their sources, function, and potential health risks.

The Importance of One-Carbon Metabolism

At a cellular level, B12 and folate are essential coenzymes in a process known as one-carbon metabolism. This metabolic pathway is critical for generating methionine from homocysteine. Methionine is an essential amino acid used in the synthesis of new proteins and DNA methylation—a fundamental biological process for regulating gene expression. Folate transfers a methyl group to vitamin B12, which, in turn, passes it to homocysteine, converting it to methionine. A deficiency in either vitamin can disrupt this process, leading to a build-up of homocysteine in the blood, which is associated with an increased risk of cardiovascular disease.

Unpacking the Key Differences

Dietary Sources: Animal vs. Plant

Vitamin B12 is found almost exclusively in animal products, like meat, fish, poultry, eggs, and dairy. Fortified foods like nutritional yeast and breakfast cereals are also sources for those on plant-based diets. Folate is abundant in plant and animal foods, including dark leafy greens, legumes, nuts, citrus fruits, and eggs. Vegans and vegetarians may be at higher risk for B12 deficiency without fortification or supplementation.

Bioavailability and Absorption

B12 absorption requires intrinsic factor from the stomach. Conditions affecting the stomach, such as atrophic gastritis or pernicious anemia, can impair B12 absorption. Folate absorption differs; the body absorbs natural folate and converts synthetic folic acid (often in fortified foods) to its active form, 5-MTHF, a process influenced by genetic factors like the MTHFR polymorphism.

The Consequences of Deficiency

Deficiencies in both vitamins can cause megaloblastic anemia, characterized by large, immature red blood cells. Both can cause fatigue, weakness, and shortness of breath. However, B12 deficiency uniquely risks severe, potentially irreversible neurological damage. B12 deficiency symptoms can include tingling/numbness, difficulty walking, memory issues, depression, and paranoia. Folate deficiency symptoms include anemia-related issues, a sore tongue, mouth sores, irritability, and diarrhea. Severe maternal folate deficiency is a major cause of neural tube defects.

B12 and Folate at a Glance: A Comparison Table


Feature	Vitamin B12 (Cobalamin)	Folate (Vitamin B9)
Primary Function	Essential for DNA synthesis, red blood cell formation, and nervous system maintenance.	Essential for DNA synthesis, cell division, and repair.
Dietary Sources	Found almost exclusively in animal products like meat, fish, eggs, and dairy.	Abundant in leafy green vegetables, legumes, nuts, and fortified grains.
Absorption Mechanism	Requires intrinsic factor produced in the stomach for proper absorption in the small intestine.	Absorbed directly in its natural form (folate) or synthetic form (folic acid), though some need a specific enzyme (MTHFR) for conversion.
Body Storage	Stored in large quantities in the liver, with reserves lasting several years.	Stored in smaller quantities in the liver, with reserves lasting only a few months.
Neurological Effects of Deficiency	Can cause severe and often irreversible nerve damage, including tingling, numbness, and cognitive issues.	Generally does not cause neurological damage, but deficiency can cause fatigue and irritability.
Masking of Deficiency	High folic acid intake can mask the megaloblastic anemia caused by a B12 deficiency, allowing neurological damage to worsen undetected.	Does not mask B12 deficiency.
Who is at Risk?	Older adults, vegans, vegetarians, and individuals with gastrointestinal disorders like pernicious anemia.	Pregnant women, individuals with alcohol use disorder, those with malabsorption issues, and people with certain genetic mutations.

Conclusion

B12 and folate are vital but distinct B vitamins. B12's unique absorption needs and critical role in nerve health mean it cannot replace folate. A key concern is that high folic acid intake can mask B12 deficiency symptoms while neurological damage progresses. Addressing both deficiencies is crucial, especially in at-risk groups like older adults, vegans, and pregnant women. Consulting a healthcare provider is essential for managing levels of these nutrients.

The B12-Folate Interdependence

Proper folate utilization requires active B12. Without B12, folate can be trapped in an inactive form, causing a functional folate deficiency despite adequate intake. This interdependence means a deficiency in one can mimic the other, and treatment for megaloblastic anemia often involves both. Healthcare providers must check B12 levels before prescribing high-dose folic acid to avoid masking a B12 deficiency.

Learn more about the B vitamins and their functions.

Fortification and Supplementation

Mandatory folic acid fortification has reduced neural tube defects but raises concerns about masking B12 deficiency in vulnerable populations. Supplementation may be needed for pregnant women, the elderly, those with GI issues, or vegans. A balanced diet is ideal, but fortified foods and medical supervision are recommended for those with specific needs to prevent deficiencies and protect health.

Frequently Asked Questions

Yes, taking high doses of folic acid (the synthetic form of folate) can mask the megaloblastic anemia that is a hallmark of B12 deficiency. By correcting the anemia, it can allow the underlying neurological damage from a B12 deficiency to progress undetected, potentially causing irreversible harm.

Both are crucial for cellular processes, but B12 acts as a key cofactor for an enzyme that helps convert folate into its active form and is uniquely required for maintaining nerve cells. Folate is directly involved in DNA and red blood cell synthesis.

B12 is naturally found almost exclusively in animal products, meaning vegans who don't consume fortified foods or supplements are at risk. Folate, however, is abundant in a wide range of plant-based foods such as leafy greens and legumes, so deficiency is less likely from diet alone.

If you take folic acid without addressing a B12 deficiency, the anemia symptoms may improve, but the critical and more dangerous neurological damage caused by the B12 shortage will continue to worsen. This is why testing for both is important before supplementation.

B12 and folate work together in a metabolic pathway to convert homocysteine to methionine. In this process, B12 relies on folate to receive a methyl group, enabling them to produce new proteins and form healthy red blood cells.

Older adults, pregnant women, vegans, and individuals with certain gastrointestinal disorders are at a higher risk of deficiency. For pregnant women, insufficient folate is linked to neural tube defects.

The body can store a large amount of B12 in the liver, potentially lasting for several years before a deficiency becomes symptomatic. Folate, being water-soluble and stored in smaller quantities, must be replenished more frequently through daily intake.

People with absorption disorders like pernicious anemia or those who have had gastrointestinal surgery often require alternative treatments. This can include vitamin B12 injections or high-dose oral supplements to bypass the normal absorption route.