Vitamin B Complex: Benefits, Uses, Risks, And More

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Medical News TodaySubscribeBenefits and uses of B-complex vitamins

Medically reviewed by Meredith Goodwin, MD, FAAFP — Written by Jennifer Berry and Brittany Patterson — Updated on February 25, 2025

Vitamin B complex
Dosage
Benefits
Who should take them?
Risks
Choosing supplements
Interactions
Foods
Speaking with a doctor
Summary

“Vitamin B” refers to eight different vitamins, which all play a role in converting food into energy in the body. Each vitamin has a unique role in a person’s health. Vitamin B-complex supplements include all of the essential B vitamins in one pill.

Some of these supplements contain 100% of the recommended daily allowance (RDA) of every B vitamin. Others contain higher doses of some or all of these vitamins.

Many people get all the vitamin B they need from a varied, balanced diet. However, others may benefit from taking a vitamin B-complex supplement.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Learn more.

What is in the vitamin B complex?

Woman drinking water with B vitamin complex supplements — blackdovfx/Getty Images

If a product contains the vitamin B complex, it should have some of each of the following:

Vitamin B1 (thiamin): Vitamin B1 is vital to the healthy growth and function of organs, including the brain and heart.
Vitamin B2 (riboflavin): The body needs vitamin B2 to break down fats and drugs.
Vitamin B3 (niacin): The body needs niacin to maintain healthy skin, nerves, and digestion. Doctors sometimes prescribe high doses of niacin to help manage cholesterol levels.
Vitamin B5 (pantothenic acid): Vitamin B5 is essential for the health of the brain and nervous system.
Vitamin B6 (pyridoxine): Vitamin B6 helps the body make new red blood cells, which carry oxygen throughout the body. It also helps keep the immune system strong.
Vitamin B7 (biotin): Biotin is essential for healthy hair, nails, and nerve function.
Vitamin B9 (folic acid): The body uses folic acid — or folate, its natural form — to make DNA and genetic material. Before and during pregnancy, sufficient amounts of folic acid help reduce the risk of certain developmental issues for a fetus.
Vitamin B12 (cobalamin): The body’s nerve and blood cells require vitamin B12. Adequate levels of B12 also prevent pernicious anemia, which is a deficiency of this nutrient.

Further resources

For more in-depth resources about vitamins, minerals, and supplements, visit our dedicated hub.

Daily recommendations for a vitamin B-complex supplement

Many B-complex supplements contain about 100% of the RDA of each of the eight B vitamins.

However, some contain very high levels of certain B vitamins. Before taking a high dose supplement, talk with a doctor.

The following are RDAs for each of the B vitamins, in milligrams (mg) or micrograms (mcg), according to the Office of Dietary Supplements. Older adults may require higher dosages of some B vitamins.

Males	Females	During pregnancy	During breastfeeding
Vitamin B1	1.2 mg	1.1 mg	1.4 mg	1.4 mg
Vitamin B2	1.3 mg	1.1 mg	1.4 mg	1.6 mg
Vitamin B3 or dietary equivalents	16 mg	14 mg	18 mg	17 mg
Vitamin B5	5 mg	5 mg	6 mg	7 mg
Vitamin B6 (adults ages 19 to 50)	1.3 mg*	1.3 mg*	1.9 mg	2.0 mg
Vitamin B7	30 mcg	30 mcg	30 mcg	35 mcg
Vitamin B9 or dietary equivalents	400 mcg	400 mcg	600 mcg	500 mcg
Vitamin B12	2.4 mcg	2.4 mcg	2.6 mcg	2.8 mcg

*The National Institutes of Health (NIH) advises that male adults ages over 51 years require 1.7 mg and female adults over 51 require 1.5 mg.

Benefits and uses of a vitamin B-complex supplement

Vitamin B-complex supplements may help with certain health problems. However, people should always speak with a doctor before taking any supplements.

If a person has any of the conditions listed below, they may benefit from taking a supplement that contains B vitamins:

Migraine

A 2022 randomized double-blind controlled trial found that certain B vitamins could help treat and prevent migraine episodes as an adjunctive treatment, specifically:

However, the researchers also suggest that further large-scale long-term studies into this topic are necessary.

A 2022 systematic review and meta-analysis also found that taking 400 mg of vitamin B2 supplements daily for 3 months significantly decreased the duration, frequency, and pain score of migraine attacks.

Depression and anxiety

Authors of a study from 2018 state that there is a correlation between vitamin B12 levels and the development and presentation of depression and anxiety.

They report that participants with depression or anxiety had lower levels of B12 than their control counterparts, potentially suggesting a relationship between the two. However, more research is needed.

A 2023 study involving adolescents had similar findings.

A small-scale 2019 study in India also suggested that B9 and B12 deficiencies could play a role in depression and anxiety, though the increased risk shown was not significant.

Additionally, a 2021 study including 7,387 adults in Iran ages 20 to 70 years suggested that a higher intake of dietary B vitamins, particularly biotin, was associated with a lower prevalence of depression, anxiety, and stress symptoms.

However, the study authors noted that further research into how B vitamins may affect mental health is necessary.

Skin wounds

B vitamins may help the skin heal.

One study found that, when applied to the skin, these vitamins could help wounds heal more effectively.

An animal study found that B12 improved wound healing in mice with diabetes, and another study in pigs found that applying vitamin B12 ointment to treat radiation dermatitis lesions was highly effective. However, research on humans is needed.

Canker sores

Vitamin B12 may be useful in helping treat canker sores, also known as oral ulcers.

A 2020 review noted that topical application of B12 ointment may help treat recurrent canker sores. However, the authors noted that large-scale high-quality research into this topic is lacking.

Premenstrual syndrome

A 2023 review noted that some studies have found micronutrients including B vitamins effective in reducing premenstrual syndrome (PMS).

However, evidence is too insufficient and limited to support their use as an effective treatment. Further research is necessary.

Who should take B-complex vitamins?

The following sections look at who may benefit from taking vitamin B-complex supplements.

Pregnant people

B vitamins are particularly important during pregnancy, when a person should take in at least 400 mcg of folic acid every day.

Ideally, this would also occur in the months before getting pregnant. Some people require the use of methylated folate due to a MTHFR gene variant that can prevent folic acid from breaking down.

In addition, pregnant people need to consume folate — the natural form of folic acid — from food sources. Getting the recommended amounts of folic acid and folate reduces the risk of developmental issues for a fetus involving the brain and spinal cord, according to the Centers for Disease Control and Prevention (CDC).

Pregnant people also need plenty of vitamin B12. Studies show that vitamin B12 deficiency has an association with early pregnancy loss, low birth weight, high blood pressure in the pregnant person, and fetal abnormalities.

Vegetarians and vegans

Vegetarian and vegan diets can increase a person’s risk of B12 deficiency. B12 is present in many animal-based foods, including meat, eggs, and dairy.

People who eat eggs and dairy products may be getting the B12 that they need from these foods. However, those who eat no animal products may need supplements.

People who have had gastric bypass surgery

Individuals who have undergone gastric bypass surgery, also known as bariatric surgery, often need vitamin supplements.

Research indicates that this surgery increases a person’s need for B12. There is further evidence from 2016 that many people need a multivitamin that includes B vitamins and other nutrients after this surgery, at least in the short term.

Older adults

People who are 65 or older may benefit from a B-complex supplement.

Research from 2010 suggests older adults are more susceptible to vitamin B12 deficiency. Some evidence from 2016 suggests that having higher levels of B12 may help slow the aging of the brain. However, confirming this finding requires further research.

Low levels of B12 and folate — a dietary equivalent of folic acid, or vitamin B9 — may be associated with depression in older people, according to a 2014 systematic review and meta-analysis.

In addition, a 2018 study involving older Latino adults found that higher B6 levels were linked to decreased depression symptoms.

A 2023 study notes that vitamin B12 supplements may help improve cognitive function in older adults with cognitive impairment.

People with other health conditions

A person with any of the following health conditions may benefit from a vitamin B-complex supplement:

alcohol use disorder
an autoimmune condition, such as lupus, rheumatoid arthritis, or type 1 diabetes
depression
diabetes
a malabsorption condition, such as celiac disease or Crohn’s disease
kidney disease
HIV
heart disease
Alzheimer’s disease
AIDS
cancer

Side effects and risks of vitamin B-complex supplements

B vitamins are water-soluble. This means that, most of the time, the body excretes extra B vitamins in the urine.

While a standard dosage does not seem to cause harm, excessively high doses of certain B vitamins can be dangerous. It is important to speak with a clinician before taking very high doses of B-complex supplements.

Possible side effects and risks of B-complex vitamins include:

High blood sugar: High doses of nicotinic acid, a synthetic form of vitamin B3, can raise blood sugar levels. This can interfere with diabetes medications. People with diabetes or high blood sugar should not take doses of nicotinic acid measuring 1,500 mg or more.
Excess nicotinic acid: Too much nicotinic acid can also cause low blood pressure, fatigue, headaches, rashes, and liver damage.
Excess nicotinamide: High doses of nicotinamide, another form of vitamin B3, can cause diarrhea and increased bleeding. This can occur with doses of 500 mg per day. Doses higher than 3,000 mg can cause vomiting and liver damage.
Excess folic acid: Taking more than 1,000 mcg of folic acid a day can mask a type of anemia caused by vitamin B12 deficiency.

Taking a high dose B-complex supplement can also turn a person’s urine bright yellow. This effect is temporary and harmless. Once the kidneys get rid of the extra vitamins, the color will return to normal.

Choosing the right vitamin B-complex supplement

A doctor may recommend a certain type of vitamin B-complex supplement, depending on a person’s health needs.

Some vitamin and supplement companies use independent quality testing of their products. Those that pass may have a seal of approval from an independent testing organization.

This seal does not guarantee that the product is 100% safe or effective for everyone. However, it means that the product contains what is listed on the label without contaminants.

Some testing organizations and their certifications include:

ConsumerLab.com’s approved quality product seal
NSF International’s dietary supplement certification
the verified mark of the United States Pharmacopeial Convention (USP)

Interactions with vitamin B-complex supplements

In most cases, vitamin B does not interact negatively with other medications. However, certain medications can make a vitamin B deficiency more likely.

These are some examples of medications that can result in low levels of specific B vitamins:

Blood pressure drugs and chemotherapy drugs can lower a person’s B1 levels.
Antiseizure medications to treat epilepsy can lower B3, B6, and B9 levels.
Drugs that treat tuberculosis can cause low levels of B3 and B6.
Certain cancer drugs can lower B9 levels.
Certain drugs that treat ulcerative colitis can cause low levels of vitamin B9.
Certain antibiotics and medications for ulcers, diabetes, or gastroesophageal reflux disease (GERD), may lower B12 levels.

Which foods contain B vitamins?

Some foods contain several B vitamins. A person needs a varied diet to consume all eight types.

People can get all the B vitamins that they need from omnivorous, vegetarian, or vegan diets.

However, animal products are a major source of B vitamins. So, people following restricted diets should take steps to ensure that they are getting enough of each vitamin from different dietary sources.

Some of the best food sources of B vitamins include:

beef
pork
fish
organ meats
avocados
leafy greens
nuts
legumes
whole grains
milk
cheese
yogurt
enriched and fortified breads and cereals
mushrooms

When to speak with a doctor

Anyone who is at higher risk of having a vitamin B deficiency should talk with a medical professional.

People with certain health conditions including HIV, alcohol use disorder, and Crohn’s disease may not absorb vitamin B effectively. Older individuals and people who eat a vegetarian or vegan diet may also be at higher risk.

Symptoms of a vitamin B deficiency will vary depending on what B vitamin a person is lacking.

A person with a vitamin B12 deficiency may experience:

tingling in the hands or feet
fatigue
pale skin or jaundice
shortness of breath
fast heartbeat
mouth ulcers, burning, or pain
cognitive impairment
digestive issues including diarrhea, vomiting, and nausea, which may lead to weight loss
irritability or depression

A doctor may conduct a blood test to confirm a vitamin B deficiency.

Summary

Whenever possible, a person should try to get sufficient B vitamins by eating a variety of healthy foods. However, some people may benefit from taking a B-complex supplement.

People can find these supplements in health or drug stores, or they can choose between brands online.

A B-complex supplement is generally safe when a person takes it as directed. However, only take very high doses of B vitamins under a doctor’s guidance.

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How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

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Medically reviewed by Meredith Goodwin, MD, FAAFP — Written by Jennifer Berry and Brittany Patterson — Updated on February 25, 2025

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