Folic Acid Is Which Vitamin? Vitamin B9 Explained

Folic acid is vitamin B9. More precisely, "vitamin B9" is a common name for folate, the family of related compounds, and folic acid is one specific manufactured form of it used in supplements and fortified foods.¹² It is not iron, vitamin B12, or vitamin B6, even though these nutrients often appear together on the same label.³²

This page explains how the vitamin B9 names fit together, how folic acid compares with the other forms, what the vitamin does, how much you need, and how to avoid common mix-ups.

Is folic acid vitamin B9?

Yes. CDC uses "vitamin B9" as a common name for folate, and folic acid is one form of that vitamin.¹ Think of it like this:

• Vitamin B9 and folate are the family name.¹²
• Folic acid is one member of that family, made for supplements and fortified foods.²
• Food folates, 5-MTHF (methylfolate), and folinic acid are other members, each with different uses.²⁴

Folic acid is the fully oxidized form of folate. It is more stable and generally better absorbed than the folate that occurs naturally in food.² That stability is the main reason it is used to fortify grain products and fill most supplements.²

The vitamin B9 family: forms compared

Not every form of vitamin B9 is interchangeable. Each has different evidence and different uses.⁴²

Two points come up often enough to repeat. First, methylfolate is a legitimate form of folate, but CDC still recommends folic acid for preventing neural tube defects because it is the only form directly proven for that outcome.⁷¹ Our comparison of methylfolate vs folic acid covers the details.

Second, folinic acid (leucovorin) is a reduced folate drug, not another name for ordinary folic acid.⁴ See folinic acid vs folic acid for how clinicians use it.

Folic acid vs folate: why the names get mixed up

Folate is the general name for vitamin B9 and includes both natural food folates and manufactured forms.² Folic acid is one specific form used in fortified foods and supplements.¹ In everyday speech people use the words loosely, and many labels and articles do the same.

The difference matters for three practical reasons:

1. Absorption. About 50% of food folate is absorbed, compared with at least 85% of folic acid taken with food.²
2. Labels. U.S. labels list total folate in mcg DFE and show added folic acid in parentheses, so you need to know which number you are reading.²
3. Pregnancy. Folic acid is the only form of folate shown in studies to help prevent neural tube defects.⁵

For the full breakdown, see folate vs folic acid.

What folic acid is not: iron, B12, and B6

Folic acid is vitamin B9. It is not iron, vitamin B12, or vitamin B6.³² Prenatal and anemia products often combine these nutrients because each has a distinct role in blood formation or pregnancy, but a combined label does not make them interchangeable.³²

Why B9 and B12 are easy to confuse

Vitamin B12 and folate are both needed to make healthy red blood cells.³ A shortage of either can cause similar symptoms, and folate deficiency signs overlap with B12 deficiency, iron deficiency, and other conditions.⁸³

That overlap has a safety angle. Large amounts of folate can correct the anemia of vitamin B12 deficiency without treating the nerve damage it causes.⁹² This is why NIH advises checking B12 when megaloblastic anemia or nerve symptoms are possible, rather than treating with folic acid alone.⁹² At recommended intakes, CDC notes that folic acid fortification has not been shown to delay detection of B12 deficiency.¹⁰ Read more in folic acid and vitamin B12.

What does vitamin B9 do?

Folate carries one-carbon units that the body needs to make DNA and RNA and to process amino acids.² It also helps convert homocysteine to methionine and produce S-adenosylmethionine, a major methyl donor.²

These jobs matter most where cells divide quickly, such as in a developing embryo and in red blood cell production. When folate is short, DNA formation is disrupted and megaloblastic anemia can develop.² CDC describes folic acid as supporting the production of new cells, including blood, brain, skin, hair, and nail cells.¹

How much vitamin B9 do you need?

Vitamin B9 needs are given in mcg DFE (Dietary Folate Equivalents), which adjust for how well each form is absorbed.²

Source: NIH Office of Dietary Supplements.²

On top of these general targets, CDC recommends 400 mcg of folic acid daily for everyone who could become pregnant, from supplements, fortified foods, or both.¹¹¹ Our guide to folic acid for pregnancy explains the timing. USPSTF recommends 400 to 800 mcg a day starting at least one month before conception.¹²

The adult upper limit is 1,000 mcg a day of folic acid from supplements and fortified foods. It does not apply to natural food folate.²

Reading vitamin B9 on a supplement label

Supplement labels in the U.S. list total folate in mcg DFE. When folic acid is added, the label shows the folic acid amount in parentheses.² That is why the same tablet can say "667 mcg DFE (400 mcg folic acid)": 400 mcg of folic acid taken with food equals about 667 mcg DFE.²

Products using 5-MTHF are harder to compare. No formal DFE conversion factor has been set for supplemental 5-MTHF, and FDA lets manufacturers use a factor comparable to folic acid or another supported factor of up to 1.7.² So two products with the same DFE number on the front may contain different forms and different actual amounts.²

Where to get vitamin B9

Natural folate is found in leafy vegetables, beans and peas, asparagus, Brussels sprouts, avocado, citrus, nuts, liver, eggs, seafood, dairy, meat, poultry, and grains.⁵² Folic acid comes from enriched or fortified foods and from supplements.²

A few examples: 1/2 cup of boiled spinach provides 131 mcg DFE, 1/2 cup of boiled black-eyed peas provides 105 mcg DFE, and 1/2 cup of cooked enriched white rice provides 90 mcg DFE.² Folic acid is sold alone and in multivitamins, B-complex products, and prenatal vitamins, commonly at 400 to 800 mcg.²

This article is for general education and is not medical advice. Doses and needs differ from person to person, so talk with your clinician or pharmacist about your situation. Read our editorial policy and medical disclaimer.