Should vitamin B12 and folate be taken together? The symbiotic relationship and crucial risks

October 8, 2025 •

4 min read

Approximately 12.5% of US adults have vitamin B12 insufficiency, while folate is critical for DNA and red blood cell production. Given their intertwined metabolic roles, a common question arises: Should vitamin B12 and folate be taken together?. The answer depends heavily on your health status and the form of supplementation, as a serious risk exists.

Quick Summary

Vitamin B12 and folate are essential B vitamins that function synergistically for DNA synthesis and nerve health. High synthetic folic acid intake can mask a B12 deficiency, potentially allowing irreversible neurological damage to progress unnoticed.

Key Points

Synergy is key: Vitamin B12 and folate are metabolically linked and rely on each other for functions like DNA synthesis and homocysteine metabolism.
Masking is a serious risk: High doses of synthetic folic acid can hide the blood symptoms of a B12 deficiency, allowing severe, irreversible neurological damage to advance unnoticed.
Always test first: Before taking high-dose folate, get your vitamin B12 levels checked by a healthcare provider to rule out a hidden deficiency.
Older adults are vulnerable: As B12 absorption declines with age, older adults on high-folic acid supplements face a higher risk of accelerated mental and neurological decline.
Combined supplements can be safe: Many combination supplements provide balanced doses of both vitamins, but medical supervision is advised to prevent imbalance.
Pregnant women need both: Adequate levels of both B12 and folate are essential during pregnancy for fetal development and to reduce the risk of birth defects.
Natural vs. synthetic matters: Natural folate from food does not pose the same masking risk as high-dose synthetic folic acid supplements.
Specific groups need caution: Individuals with GI disorders, vegans, and those on certain medications must be particularly careful about their intake and monitoring.

The Synergistic Relationship Between B12 and Folate

Vitamin B12 and folate (or vitamin B9) are part of the B-vitamin family and are metabolically linked. They function as a team to support various critical processes in the body. Their most notable co-dependent function is in the methylation cycle, a biochemical process essential for DNA synthesis and repair, as well as the production of neurotransmitters. Specifically, vitamin B12 is needed to recycle folate's active form, 5-methyltetrahydrofolate (5-MTHF), allowing it to participate in further reactions.

This partnership is also vital for the metabolism of homocysteine, an amino acid. High levels of homocysteine are linked to an increased risk of cardiovascular disease. Together, B12 and folate help convert homocysteine back into methionine, thus maintaining healthy levels and supporting heart health. Deficiencies in either vitamin can disrupt this process, leading to a build-up of homocysteine.

Their cooperative role is also critical for hematological health, as both are necessary for the formation of healthy red blood cells. A deficiency in either vitamin can result in megaloblastic anemia, a condition characterized by abnormally large and immature red blood cells.

The Critical Risk: High Folic Acid Masking a B12 Deficiency

While the synergistic relationship is beneficial, a significant risk arises when high doses of synthetic folic acid (the form of B9 used in supplements and fortified foods) are taken without addressing an underlying B12 deficiency. This is known as the "masking effect".

The danger lies in how the body's systems compensate. When a B12 deficiency is present, a person may develop megaloblastic anemia and experience symptoms like fatigue and weakness. High-dose folic acid can correct this anemia and resolve these physical symptoms, essentially hiding a key indicator of the B12 problem. However, it does not correct the underlying B12 deficiency, and the neurological damage caused by a lack of B12 can continue to progress, potentially becoming irreversible.

This is particularly concerning for vulnerable populations, such as older adults, who are more susceptible to both B12 deficiency and neurological decline. Many older individuals have reduced stomach acid, which impairs the absorption of B12 from food, but not necessarily from synthetic folic acid. This makes them particularly prone to the masking effect if they self-supplement incorrectly. The risk is primarily associated with high doses of synthetic folic acid, not natural folate from whole foods.

Who Needs to Be Cautious About Combined Supplementation?

Certain individuals should be especially mindful of their B12 and folate intake and consult a healthcare provider before starting supplementation.

Older Adults: As mentioned, absorption issues increase with age. It is vital for this group to get their B12 status checked and address any deficiencies directly.
Vegans and Vegetarians: Natural vitamin B12 is found almost exclusively in animal products, placing those on plant-based diets at higher risk of deficiency.
Individuals with Gastrointestinal Disorders: Conditions like Crohn's disease, celiac disease, or a history of gastric surgery can impair the absorption of B12.
People Taking Certain Medications: Some drugs, including metformin and proton pump inhibitors, can interfere with B12 absorption.

Best Practices for Taking B12 and Folate

For those considering supplementation, following a prudent strategy is essential to reap the benefits while avoiding risks.

Consult a Healthcare Provider: Always get your vitamin B12 and folate levels checked via a blood test before starting supplementation.
Choose the Right Forms: Look for supplements containing methylated folate (L-Methylfolate) and methylcobalamin (a bioavailable form of B12). These forms are often more readily absorbed by the body.
Consider Combined Supplements: For those without a hidden B12 deficiency, a balanced combination supplement formulated to prevent imbalances can be an effective way to ensure adequate intake of both vitamins.

Comparison of Supplementation Strategies


Feature	Combined B12 and Folate Supplementation	High-Dose Folate (without B12 check)
Key Benefit	Comprehensive support for methylation, DNA, and red blood cells; avoids imbalance.	Corrects megaloblastic anemia symptoms caused by folate deficiency.
Primary Risk	Minimal risk of imbalance if levels are tested and supplementation is medically supervised.	Masks a hidden B12 deficiency, allowing irreversible neurological damage to progress.
Recommended For	Individuals with confirmed deficiencies in both, or those at risk who are medically monitored.	Should only be used for confirmed folate deficiency after ruling out B12 deficiency; high doses should not be used as a substitute for B12 treatment.
Best Practice	Consult a doctor for blood tests to ensure balanced supplementation.	Never self-medicate high-dose folate without a doctor ruling out B12 deficiency.

Understanding the Differences: Natural Folate vs. Synthetic Folic Acid

It is important to distinguish between naturally occurring folate and synthetic folic acid. Folate is found in foods like leafy green vegetables, citrus fruits, and beans. The risk of masking a B12 deficiency is not associated with dietary folate intake. Folic acid is the synthetic, more stable form used to fortify foods and in many supplements. The liver can only process a certain amount of folic acid at a time, and excess intake can lead to unmetabolized folic acid in the bloodstream.

Conclusion

The question, "Should vitamin B12 and folate be taken together?" is best answered with a conditional "yes." On one hand, the two vitamins are a powerful, synergistic duo for essential bodily functions like methylation, DNA synthesis, and red blood cell production. On the other hand, the critical risk of high-dose synthetic folic acid masking a dangerous B12 deficiency means unmonitored supplementation should be approached with extreme caution, especially in at-risk populations like older adults. A safe approach requires medical consultation and proper testing to ensure any B12 issues are addressed directly. Informed, guided supplementation is key to harnessing the benefits of this nutritional partnership without falling victim to its hidden dangers.

Authoritative Source

Health Professional Fact Sheet on Vitamin B12 from the National Institutes of Health.

Frequently Asked Questions

Yes, they can be taken together and often are, as they work synergistically. However, it is crucial to ensure that you do not have an undiagnosed vitamin B12 deficiency, especially if you are taking high-dose folic acid, as it can mask the symptoms.

The masking effect occurs when high doses of synthetic folic acid correct the megaloblastic anemia (abnormally large red blood cells) caused by a B12 deficiency, but do not address the neurological damage. This allows the nerve damage to progress undetected.

Common symptoms include fatigue, weakness, a sore or red tongue, and mouth ulcers. A B12 deficiency specifically can also cause neurological issues like pins and needles, balance problems, and cognitive changes.

Both vitamins are vital for DNA synthesis and cell division. Adequate intake of folate (as folic acid) before and during early pregnancy is crucial to reduce the risk of neural tube defects like spina bifida.

Older adults, vegans/vegetarians, and people with gastrointestinal disorders like Crohn's disease or celiac disease are at higher risk. Individuals who have undergone gastric surgery or take certain medications are also susceptible.

A combination supplement can be effective, especially if you have a known deficiency in both. However, consulting a healthcare professional is best to determine the appropriate dosage and ensure no underlying B12 issues are missed.

Yes. Folate is the naturally occurring form found in foods, while folic acid is the synthetic form used in supplements and fortified foods. The masking risk is associated with high doses of synthetic folic acid, not natural folate from food.