What Does Taking B12 and Folic Acid Do? Your Guide to Synergistic Benefits

November 20, 2025 •

4 min read

Did you know that a deficiency in either vitamin B12 or folate can lead to a condition called megaloblastic anemia, where the body produces abnormally large red blood cells? Understanding what does taking B12 and folic acid do is crucial, as these vitamins play complementary roles in numerous physiological processes that are essential for good health.

Quick Summary

This guide explains the synergistic functions of vitamin B12 and folic acid in the body. It covers their combined roles in energy metabolism, nerve health, DNA synthesis, and red blood cell formation, clarifying their importance for overall wellness.

Key Points

Synergistic Action: Vitamin B12 and folic acid work together in the methylation cycle, where B12 activates folate, making it crucial for DNA synthesis and cellular function.
Prevents Megaloblastic Anemia: A deficiency in either vitamin can cause this specific type of anemia, leading to fatigue and weakness, which can be corrected with proper intake.
Protects Nerve Health: B12 is essential for maintaining the myelin sheath that protects nerves, while folate helps in neurotransmitter synthesis, both of which support neurological function.
Vital for Fetal Development: Adequate intake is critical during pregnancy to prevent neural tube defects such as spina bifida.
Regulates Homocysteine Levels: The combination helps convert homocysteine to methionine, which supports cardiovascular health.
Supports Energy Metabolism: Both vitamins aid in converting food to usable energy, and a deficiency can lead to fatigue.
Masking Risk: High doses of folic acid can mask the symptoms of a vitamin B12 deficiency, which can be dangerous if the underlying issue is not addressed.

The Powerful Partnership of B12 and Folic Acid

Vitamin B12 and folic acid (vitamin B9) are not just two separate nutrients; they are metabolic partners that rely on each other to perform critical functions within the body. Their most significant interaction occurs in a process known as the methylation cycle. In this cycle, vitamin B12 is necessary to activate folate, allowing it to contribute methyl groups for synthesizing DNA and producing essential neurotransmitters. Without sufficient vitamin B12, folate can become 'trapped' in an inactive form, leading to a functional deficiency even if dietary intake is adequate. This intricate dance is fundamental to cellular health and overall well-being.

Supporting Red Blood Cell Formation and Preventing Anemia

One of the most well-known functions of taking B12 and folic acid is their combined role in producing healthy red blood cells. When deficient in either vitamin, the body cannot create functional red blood cells, leading to a type of anemia called megaloblastic anemia. This condition is characterized by large, immature, and fewer-than-normal red blood cells, which are less effective at carrying oxygen throughout the body. Symptoms often include extreme tiredness, shortness of breath, and pale skin. Appropriate supplementation can reverse this condition, restoring normal red blood cell production and alleviating related symptoms.

Promoting Neurological and Cognitive Health

The health of your nervous system is heavily dependent on adequate levels of vitamin B12 and folate. Vitamin B12, also known as cobalamin, is crucial for the formation and maintenance of the myelin sheath, the protective layer surrounding nerve fibers. Damage to this sheath can impair nerve function and lead to neurological issues such as numbness, tingling, vision problems, and cognitive decline. Folic acid supports neurological health by aiding in the synthesis of neurotransmitters that regulate mood and cognitive function. For older adults with cognitive impairment, combined supplementation has shown promising results in improving performance.

Aiding DNA Synthesis and Repair

At the very core of cell life, B12 and folic acid are instrumental in DNA synthesis and repair. Folate provides the one-carbon units necessary for synthesizing the building blocks of DNA (purines and pyrimidines). In tandem with vitamin B12, it ensures accurate and efficient cell division, which is particularly vital during periods of rapid growth, such as pregnancy. Deficiency can lead to genomic instability and an increased risk of DNA damage. This cellular support is fundamental to maintaining the body's integrity and preventing disease.

The Importance During Pregnancy and Fetal Development

For pregnant individuals, the intake of B12 and folic acid is paramount. Good levels of these vitamins are known to significantly reduce the risk of neural tube defects (NTDs) in the developing fetus, such as spina bifida and anencephaly. Folic acid supplementation is especially critical in the early stages of pregnancy, often before the individual is even aware they are pregnant. The synergistic action of B12 and folate supports proper cell growth and division, which is essential for the healthy development of the baby's brain and spinal cord.

How B12 and Folic Acid Impact Heart Health

The combined action of B12 and folic acid is a powerful tool for maintaining cardiovascular health by regulating homocysteine levels. High levels of this amino acid are associated with an increased risk of heart disease and stroke. Together, these vitamins help convert homocysteine into methionine, an essential amino acid, thereby lowering homocysteine concentrations in the blood. While the evidence for reducing heart disease incidence is mixed, studies do show a clear effect on reducing homocysteine and possibly reducing stroke risk.

Food Sources for a Balanced Diet

It is possible to get sufficient amounts of B12 and folate from a balanced diet. However, certain groups may require supplementation. Vegans, for example, must supplement B12 as it is primarily found in animal products. Conversely, folate is found naturally in a wide array of plant-based foods. Here are some key sources for both:

Natural Sources of Folate (B9)

Leafy green vegetables (spinach, kale)
Legumes (chickpeas, lentils, peas)
Asparagus and broccoli
Fruits (oranges, bananas, papaya)
Fortified cereals, breads, and pasta

Natural Sources of Vitamin B12

Meat (beef, poultry)
Fish and shellfish (salmon, clams)
Dairy products (milk, cheese, eggs)
Nutritional yeast (fortified)
Fortified cereals

Comparison of B12 and Folic Acid Functions


Feature	Vitamin B12 (Cobalamin)	Folic Acid (Vitamin B9)
Primary Role	Nerve health, red blood cell formation, DNA synthesis	Cell growth, red blood cell formation, DNA synthesis
Synergistic Action	Activates folate for cellular processes	Is activated by B12 to function in methylation
Key Benefit	Maintains myelin sheath for nerve function	Crucial for preventing neural tube defects in fetus
Absorption	Requires Intrinsic Factor in stomach	Absorbed more readily from supplements than food
Storage	Stored in the liver for years	Stores last for months, requires daily intake
Key Deficiency Risk	Neurological damage if untreated	Anemia, birth defects, high homocysteine
Food Sources	Animal products, fortified foods	Leafy greens, legumes, fortified foods

Conclusion

The combined intake of B12 and folic acid is fundamental to a vast array of bodily functions, underpinning everything from cellular metabolism to the health of the nervous system. From preventing specific types of anemia and supporting fetal development to protecting cognitive function and regulating heart health, these two B vitamins are an essential team. While a balanced diet is the best approach to nutrient intake, certain populations may require supplementation. It is important to consult a healthcare provider to determine the right dosage and approach, especially given the risk of high folic acid intake masking an underlying B12 deficiency. This proactive health management can help ensure a robust and functional body for years to come. For more detailed information, consult authoritative sources like the CDC or NIH.

Visit the CDC for more information on folic acid safety

Frequently Asked Questions

Yes, taking vitamin B12 and folic acid together is recommended for many physiological processes, as they work synergistically. However, it's crucial to ensure you don't use high doses of folic acid to treat anemia without first checking your B12 levels, as this can mask a B12 deficiency.

Symptoms of a combined deficiency can include extreme fatigue, lack of energy, a sore and red tongue, mouth ulcers, muscle weakness, vision problems, and cognitive issues such as memory problems.

B12 plays a key role in activating folic acid within the body. Without enough B12, folic acid can become trapped in an unusable form, leading to a functional folate deficiency, even if you are getting enough folate from your diet.

Groups at higher risk include pregnant women, vegans and vegetarians, older adults, and individuals with gastrointestinal conditions like Crohn's disease or celiac disease that affect nutrient absorption.

High intake of folic acid can treat the anemia caused by a B12 deficiency but can leave the neurological symptoms untreated. If the B12 deficiency goes undiagnosed, it can lead to irreversible nerve damage.

These two vitamins work together to regulate homocysteine levels in the blood. By helping convert homocysteine into a different amino acid, they can help lower high homocysteine levels, which are linked to an increased risk of heart disease.

Yes, inadequate levels of folate, and potentially B12, during the early stages of pregnancy can increase the risk of serious birth defects known as neural tube defects, such as spina bifida.