What Does It Mean If Your Folic Acid Is High?

October 23, 2025 •

3 min read

While folate is essential for health, consistently elevated levels are becoming more common, especially in countries with food fortification programs. This raises the important question: what does it mean if your folic acid is high and when should you be concerned? High levels can result from various factors, including excessive supplementation, and may mask a serious vitamin B12 deficiency.

Quick Summary

High folic acid levels most commonly result from over-supplementation or excessive intake of fortified foods. This can mask a vitamin B12 deficiency, potentially leading to neurological damage, and may have other health implications. Management involves adjusting intake under medical guidance.

Key Points

Masked B12 Deficiency: A primary risk of high folic acid is that it can hide the symptoms of a serious vitamin B12 deficiency, allowing neurological damage to progress unnoticed.
Synthetic vs. Natural: High levels are typically caused by synthetic folic acid from supplements and fortified foods, not from naturally occurring folate in whole foods.
Genetic Factors: Genetic variants, such as MTHFR polymorphisms, can impair the metabolism of folic acid, contributing to elevated levels.
Common Causes: Excessive intake from supplements, particularly when combining multiple vitamins, and a high consumption of fortified grain products are common culprits.
Manage with Medical Guidance: If you have high levels, consult a doctor to test B12, review your supplement and dietary intake, and consider switching to the active form, methylfolate.
Potential Risks: Beyond masking B12 deficiency, high folic acid has been linked in some studies to accelerated cognitive decline in older adults and mixed evidence regarding cancer risk.

Understanding the Causes of High Folic Acid Levels

High folic acid levels primarily stem from taking in more synthetic folic acid than the body can effectively process. This is particularly relevant in areas where food fortification is common.

Excessive Supplementation and Fortified Foods

The most frequent cause is excessive intake from supplements and fortified foods. Combining multivitamins, B-complex supplements, or specific folic acid pills can easily lead to high levels. Likewise, regular consumption of fortified cereals, bread, and pasta significantly contributes to overall intake.

Vitamin B12 Deficiency: A Hidden Danger

A major concern with high folic acid is its ability to conceal a vitamin B12 deficiency. Both are vital for red blood cell production, and high folic acid can correct the anemia associated with B12 deficiency, thereby delaying diagnosis. This is dangerous because untreated B12 deficiency can cause irreversible neurological damage, which folic acid does not prevent. Symptoms of B12 deficiency can include numbness, tingling, and cognitive issues.

Other Contributing Medical and Genetic Factors

Beyond diet, conditions like chronic kidney disease can impair folate clearance. Genetic variations, such as in the MTHFR gene, can also affect how the body processes folic acid, potentially leading to unmetabolized folic acid accumulation. Certain medications may also play a role.

Symptoms and Potential Health Risks

While high folic acid often has no obvious symptoms, very high doses may lead to side effects.

Possible symptoms associated with high folic acid intake include:

Digestive upset (nausea, bloating)
Irritability or sleep disturbances
Skin reactions (rare)
Worsening neurological symptoms if B12 deficiency is present

Ongoing research explores other potential risks of excess folic acid. Some studies suggest a complex link to certain cancers, and it has been associated with accelerated mental decline in older adults with low B12.

Comparison of Folic Acid Sources and Metabolism


Feature	Synthetic Folic Acid	Natural Dietary Folate
Source	Supplements, fortified grains	Leafy greens, legumes
Absorption Rate	High (approx. 85%)	Lower (approx. 50%)
Processing	Requires liver conversion; can accumulate	More efficiently utilized; low risk of buildup
Risk of Excess	High with overconsumption	Very low risk
Main Concern	Masking B12 deficiency	None related to excess intake

What to Do If Your Folic Acid is High

If blood tests show high folic acid, consult a healthcare provider for evaluation, including a vitamin B12 test.

Steps under medical supervision may include:

Reduce Folic Acid Intake: Review and potentially reduce supplements and fortified foods.
Test Vitamin B12 Levels: Essential to rule out a masked deficiency.
Consider Methylfolate: Switching to the active form, 5-MTHF, may be beneficial, especially with certain genetic variants.
Emphasize Natural Folate: Increase intake of whole foods rich in natural folate, as it's better regulated by the body.
Address Underlying Issues: Manage contributing medical conditions like kidney issues.

Conclusion

High folic acid levels, typically from synthetic sources, warrant attention, mainly due to the risk of masking a serious vitamin B12 deficiency. Distinguishing between synthetic folic acid and natural folate is crucial. Work with a healthcare provider to manage intake, get necessary tests, and focus on whole-food folate sources to maintain health. Always seek medical advice before altering supplement routines, especially if pregnant or having health conditions. For more information, refer to authoritative resources like the National Institutes of Health.

NIH Office of Dietary Supplements: Folate Fact Sheet for Consumers

Frequently Asked Questions

The main concern is that high levels of synthetic folic acid can mask a vitamin B12 deficiency by correcting the related anemia. This allows neurological damage from the untreated B12 deficiency to progress silently, which is particularly risky for older adults.

No, it is highly unlikely to get too much folate from food alone. Your body absorbs natural folate less efficiently than synthetic folic acid and can regulate its absorption better. High levels typically result from overconsumption of supplements and fortified foods.

Folate is the naturally occurring form of vitamin B9 found in foods like leafy greens and legumes. Folic acid is the synthetic, man-made version used in supplements and for fortifying foods.

You should not stop taking folic acid, especially if you are pregnant or have a medical condition, without consulting a healthcare provider. A doctor can evaluate the cause and recommend a safe adjustment to your intake.

High folic acid doesn't always cause symptoms, but some people may experience side effects like digestive upset, nausea, bloating, sleep problems, or irritability, particularly with very high doses.

To lower high levels, you should work with a healthcare provider to review and potentially reduce your intake of supplements and fortified foods. Prioritizing a diet rich in natural folate from whole foods is a key strategy.

Fortified foods are products that have synthetic folic acid added to them, such as enriched breads, cereals, flour, and pasta. This is a public health measure to prevent deficiency but can contribute to high intake when combined with supplements.