What Happens to Your Body When You Start Taking Folic Acid?

October 1, 2025 •

4 min read

According to the Centers for Disease Control and Prevention (CDC), adequate folic acid intake can help prevent a type of serious birth defect called neural tube defects. But beyond this well-known benefit for pregnancy, what happens to your body when you start taking folic acid, and how does this synthetic form of vitamin B9 affect your overall health?

Quick Summary

When you start taking folic acid, your body absorbs this synthetic B9 vitamin to enhance red blood cell production, accelerate cell growth, and improve cognitive and cardiovascular health.

Key Points

Corrects Anemia: Starting folic acid rapidly helps the body produce healthy red blood cells, reversing symptoms of folate-deficiency anemia such as fatigue and weakness.
Protects Fetal Development: For women who could become pregnant, taking folic acid prevents major birth defects of the brain and spine, known as neural tube defects (NTDs).
Supports Cell Growth and Repair: This essential B vitamin is fundamental for building and repairing DNA, thereby supporting the growth of new cells throughout the body.
Reduces Homocysteine Levels: It helps lower elevated blood levels of homocysteine, an amino acid linked to an increased risk of heart disease and stroke.
Boosts Brain Health: Consistent intake is associated with improved cognitive function, better mental health outcomes, and a reduced risk of cognitive decline in older adults.
Requires Caution with B12: A critical safety point is that high intakes of folic acid can mask the symptoms of an underlying vitamin B12 deficiency, potentially leading to serious nerve damage if not properly diagnosed and treated.

The Fundamental Role of Folic Acid

Folic acid, the synthetic version of vitamin B9, plays a central role in numerous bodily functions. Primarily, it is essential for the production of healthy new cells, including the crucial red blood cells that transport oxygen throughout your body. A deficiency can lead to a condition known as folate-deficiency anemia, characterized by abnormally large, dysfunctional red blood cells. By supplementing with folic acid, your body is better equipped to perform vital cellular tasks like repairing DNA and synthesizing new proteins. The synthetic form is also more stable and easily absorbed by the body compared to natural folate found in foods, making it an effective way to quickly raise B9 levels.

Short-Term and Long-Term Effects

When you start taking folic acid, the initial effects are often seen as an improvement in addressing any existing folate deficiency. If you are anemic, you may begin to feel less fatigued and experience an increase in energy levels within a few weeks. Over the long term, consistent supplementation helps maintain healthy folate levels, contributing to sustained benefits across multiple systems. This is particularly important because folate is water-soluble, meaning your body does not store it for extended periods, and requires a regular, consistent intake.

Benefits Across Key Bodily Systems

Cardiovascular Health

One of the most significant effects of adequate folic acid intake is its role in regulating homocysteine levels. Homocysteine is an amino acid that, in high concentrations, is associated with an increased risk of heart disease and stroke. Folic acid, along with vitamins B6 and B12, helps break down homocysteine, effectively lowering its levels in the blood. Studies have shown that consistent folic acid supplementation can lead to a significant reduction in plasma homocysteine levels, thereby potentially reducing cardiovascular risk.

Brain and Cognitive Function

Research indicates a link between low folate levels and decreased brain function, as well as an increased risk for cognitive decline and dementia. Folic acid is involved in the production of neurotransmitters, which are essential for mood regulation and brain communication. For some individuals with depression, adding folic acid to their treatment regimen has been shown to improve symptoms. For older adults with cognitive impairment, supplementation may also improve some measures of brain function.

Pregnancy and Fetal Development

For women of childbearing age, starting folic acid is critical for preventing neural tube defects (NTDs) in a developing fetus. These severe birth defects, such as spina bifida and anencephaly, occur in the first few weeks of pregnancy, often before a woman knows she is pregnant. Proactive measures, such as taking folic acid before and during early pregnancy, are essential to ensure sufficient folate is available during the critical early stages of fetal development.

Potential Side Effects and Important Considerations

While generally safe, especially in standard intakes, excessive folic acid intake can cause some side effects, including nausea, bloating, and loss of appetite. The most critical risk to be aware of is the potential for high intakes of folic acid to mask a vitamin B12 deficiency. Both folate and vitamin B12 are needed for red blood cell production, and a B12 deficiency can lead to severe and irreversible nerve damage. Taking folic acid can correct the anemia symptoms of a B12 deficiency, concealing the underlying neurological issues. For this reason, it is crucial to consult a healthcare provider, especially if you are taking supplements.

What Happens When You Get Enough Folate from Food?

For some, a balanced diet rich in natural folate sources may be sufficient. Folate is found naturally in a variety of foods.

Leafy green vegetables (e.g., spinach, kale, broccoli)
Legumes (e.g., beans, lentils, chickpeas)
Fruits (e.g., oranges, bananas, papaya)
Nuts and seeds
Eggs and dairy

Since 1998, many countries have also mandated the fortification of certain grain products, such as bread and cereals, with folic acid, further helping to prevent deficiency. However, natural folate is less stable and can be destroyed by heat during cooking. Supplementation offers a more reliable and consistent way to ensure adequate intake, particularly for those with a higher need, such as pregnant women.


Feature	Natural Folate	Synthetic Folic Acid
Source	Found naturally in foods like leafy greens, legumes, and citrus fruits.	A man-made version of vitamin B9, found in supplements and fortified foods.
Absorption	Processed in the small intestine; less stable and susceptible to damage from heat.	Absorbed more easily and is more stable than natural folate.
Metabolism	Metabolized directly in the small intestine for immediate use by the body.	Metabolized by the liver and other tissues, which can lead to higher levels of unmetabolized folic acid if intake is too high.
Regulation	Intake is limited by dietary choices; very difficult to consume excessively.	Can potentially mask vitamin B12 deficiency if intake is too high.

Conclusion: A Boost for Overall Health

Starting folic acid supplementation effectively increases your body's vitamin B9 levels, triggering a cascade of positive effects from the cellular level upwards. This includes preventing and correcting folate-deficiency anemia, supporting critical fetal development, lowering cardiovascular risk factors, and benefiting cognitive function. While most people can safely incorporate folic acid, it is crucial to be mindful of potential interactions and to ensure adequate vitamin B12 intake. The decision to supplement should be discussed with a healthcare professional, who can provide guidance based on individual health needs and dietary habits.

For more information on folic acid and women's health, you can visit the Office on Women's Health website.

Frequently Asked Questions

Folic acid begins to work in your system within hours. However, if you are treating folate-deficiency anemia, it may take several weeks of consistent supplementation before you begin to feel better and notice a reduction in symptoms like fatigue.

Yes, this is a major concern with high folic acid supplementation. It can correct the anemia caused by a vitamin B12 deficiency but allows the underlying neurological damage to progress undetected, potentially causing permanent harm.

Folate is the general term for naturally occurring forms of vitamin B9 found in food. Folic acid is the synthetic, more stable version used in supplements and fortified foods, which is more readily absorbed by the body.

General recommendations for daily folate intake vary depending on age and life stage. Pregnant women or those who could become pregnant typically have increased needs. It's best to consult a healthcare provider for personalized guidance.

Good sources of natural folate include leafy green vegetables like spinach and kale, legumes such as lentils and chickpeas, fruits like oranges, and enriched grain products like cereals and breads.

Folic acid is often recommended for all women who could become pregnant, as well as individuals with a diagnosed folate deficiency. People with certain medical conditions, like kidney disease or inflammatory bowel disease, may also have increased needs.

At standard intakes, side effects are unlikely. With higher intakes, some people may experience mild issues like nausea, gas, bloating, or a bad taste in their mouth. Allergic reactions are very rare.