Vitamin B refers to not one, but eight different vitamins. All B vitamins play a role in converting food into energy in the body. Each vitamin also has a unique role in a person’s health.

Vitamin B-complex supplements include all of the essential B vitamins in one pill. Some 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.

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

Woman drinking water with B vitamin complex supplementsShare on Pinterest
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 improve 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 to reduce the risk of certain birth defects.
  • 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.

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 National Institutes of Health Office of Dietary Supplements. Older adults may require higher dosages of some B vitamins.

MalesFemalesDuring pregnancyDuring breastfeeding
Vitamin B11.2 mg1.1 mg1.4 mg1.4 mg
Vitamin B21.3 mg1.1 mg1.4 mg1.6 mg
Vitamin B3 or dietary equivalents16 mg14 mg18 mg17 mg
Vitamin B55 mg5 mg6 mg7 mg
Vitamin B6 (adults 19-50)1.3 mg*1.3 mg*1.9 mg2.0 mg
Vitamin B730 mcg30 mcg30 mcg35 mcg
Vitamin B9 or dietary equivalents400 mcg400 mcg600 mcg500 mcg
Vitamin B122.4 mcg2.4 mcg2.6 mcg2.8 mcg

*The National Institutes of Health advises that male adults over 51 require 1.7 mg and female adults over 51 require 1.5 mg.

Vitamin B-complex supplements may help with certain health problems. If a person has any of the conditions listed below, they may benefit from taking a supplement that contains B vitamins:

Migraine episodes

Some research suggests that certain B vitamins could help prevent migraine with aura, specifically:

  • vitamin B6
  • vitamin B9
  • vitamin B12

The researchers also suggest that vitamin B2 could help prevent migraine by influencing mitochondrial dysfunction, which occurs at the cellular level.

Authors of a review study from 2017 looked at the effects of vitamin B2 on migraine. They report that this vitamin is well-tolerated and effective at reducing migraine frequency in adults, though they recommend further research.

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. This could potentially suggest a relationship between the two. However, more research needs to be done.

A 2015 meta-analysis found that B vitamins could help with depression in certain cases. The researchers said that taking some B vitamins regularly for several weeks to years could reduce the risk of depression relapse.

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.

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, though more research on humans is needed to confirm these findings.

Canker sores

Vitamin B12 may be useful in helping to treat canker sores, also known as oral ulcers. A double-blind study found that a B12 ointment relieved pain better than a placebo when used as an adjunctive therapy alongside primary treatment.

PMS

Some evidence suggests that taking a combined supplement of B6 and calcium improves symptoms of premenstrual syndrome (PMS).

A systematic review and meta-analysis also found vitamin B6 to be helpful in controlling physical and psychological PMS symptoms.

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 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 should be consuming folate — the natural form of folic acid — from food sources. Getting the recommended amounts of folic acid and folate reduces the risk of birth defects 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

People who follow a vegetarian diet do not eat meat, including beef, poultry, and fish. People following a vegan diet do not eat any animal products, including meat, eggs, and dairy products.

Vegetarian and vegan diets can increase a person’s risk of B12 deficiency. The vitamin 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 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 shows that older adults are more susceptible to vitamin B12 deficiency. Some evidence 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 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.

People with other health conditions

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

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. Speak with a clinician before taking very high doses of B-complex supplements.

Possible side effects of B-complex vitamins:

  • 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 high doses of nicotinic acid (measuring 1,000 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 in 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 the urine bright yellow. This effect is temporary and harmless. Once the kidneys get rid of the extra vitamins, the color will return to normal.

A doctor may recommend a certain type of this 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)

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:

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

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:

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 with 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 or jaundice skin
  • 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.

Whenever possible, a person should try to get sufficient B vitamins by eating a variety of healthful foods as a first-line approach. However, some people 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.

Read the article in Spanish.