B-Complex Vitamins: Benefits, Side Effects, And Dosage - Healthline

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Evidence BasedBenefits, Side Effects, and Dosage of B-Complex Vitamins

Medically reviewed by Cynthia Cobb, DNP, APRN, WHNP-BC, FAANP — Written by Jillian Kubala, MS, RD — Updated on June 6, 2024

Who should take them?
Benefits
Dosage
Side effects
Bottom line

Taking a B-complex vitamin may benefit your health if you do not get enough B vitamins from other sources. This can include people who are pregnant, vegan, or have certain medical conditions.

B vitamins are a group of nutrients that play many important roles in your body. There are 8 types of B vitamins and are found in a variety of foods. This means most people get the recommended amounts of these vitamins through diet alone.

However, certain factors may mean your body needs more B vitamins. This includes:

age
pregnancy
dietary choices
medical conditions
genetics
medications
alcohol use

In these circumstances, supplementing with B vitamins may be necessary. Nutritional supplements that contain all 8 B vitamins are referred to as B-complex vitamins or vitamin B complex.

Here are the health benefits of B-complex vitamins, as well as dosage recommendations and potential side effects.

What are B-complex vitamins?

B-complex supplements usually pack all 8 B vitamins into 1 pill.

B vitamins are water-soluble, which means your body does not store them. For this reason, your diet must supply them each day. They have many important functions and are vital for maintaining good health.

Vitamin B complex supplements usually contain the following:

B1 (thiamine). Thiamine plays an essential role in metabolism by helping convert nutrients into energy. The richest food sources include pork, sunflower seeds, and wheat germ.
B2 (riboflavin). Riboflavin helps convert food into energy and also acts as an antioxidant. Foods highest in riboflavin include organ meats, beef, and mushrooms.
B3 (niacin). Niacin plays a role in cellular signaling, metabolism, and DNA production and repair. Food sources include chicken, tuna, and lentils.
B5 (pantothenic acid). Like other B vitamins, pantothenic acid helps your body obtain energy from food and is also involved in hormone and cholesterol production. Liver, fish, yogurt, and avocado are all good sources.
B6 (pyridoxine). Pyridoxine is involved in amino acid metabolism, red blood cell production, and the creation of neurotransmitters. Foods highest in this vitamin include chickpeas, salmon, and potatoes.
B7 (biotin). Biotin is essential for carbohydrate and fat metabolism and regulates gene expression. Yeast, eggs, salmon, cheese, and liver are among the best food sources of biotin.
B9 (folate). Folate supports cell growth, amino acid metabolism, the formation of red and white blood cells, and proper cell division. It can be found in foods like leafy greens, liver, and beans or in supplements in the form of folic acid.
B12 (cobalamin). Perhaps the most well-known of all the B vitamins, B12 is vital for neurological function, DNA production, and red blood cell development. B12 is found naturally in animal sources like meats, eggs, seafood, and dairy.

Although these vitamins share some characteristics, they all have unique functions and are needed in different amounts.

Summary
B-complex supplements usually contain all eight B vitamins conveniently packed into one pill.

Who should take a vitamin B complex?

Since B vitamins are found in many foods, you are most likely not at risk of developing a deficiency as long as you follow a well-rounded diet.

However, certain circumstances increase the need for B vitamins, making supplements necessary.

People who are pregnant or nursing

During pregnancy, the demand for B vitamins, particularly B12 and folate, grows. This is because they are needed to support fetal development.

In people who are pregnant or breastfeeding or chestfeeding — especially those who follow vegetarian or vegan diets — supplementing with a B-complex vitamin is crucial.

B12 or folate deficiency during pregnancy or while nursing can lead to severe neurological damage or birth defects in the fetus or infant.

Older adults

As you age, your ability to absorb vitamin B12 decreases and your appetite declines, making it difficult for some people to get enough B12 through diet alone.

The body’s ability to release B12 from food so that it can be absorbed depends on adequate amounts of stomach acid.

However, it’s estimated that many older adults don’t produce enough stomach acid to properly absorb B12. If you take medications to reduce stomach acid in order to treat acid reflux or heartburn, this can also inhibit your B12 absorption.

Those with certain medical conditions

People with certain medical conditions are more likely to develop deficiencies in nutrients like B vitamins.

This includes:

celiac disease
Crohn’s disease
alcoholism
hypothyroidism
anorexia

What’s more, people who have undergone certain weight loss surgeries are also more likely to be deficient in B vitamins.

In these circumstances, people are often advised to supplement with a B-complex vitamin to correct or prevent deficiencies.

Vegetarians and vegans

Vitamin B12 is naturally found in animal products like meat, dairy, eggs, and seafood.

Vegans and strict vegetarians could be at risk of developing a B12 deficiency if they don’t get enough of this vitamin through fortified foods or supplements.

A daily B-complex vitamin can help ensure that people who choose to follow diets that eliminate animal products are getting enough of these important nutrients.

People taking certain medications

Commonly prescribed medications can lead to a deficiency in B vitamins.

For example, proton pump inhibitors, which are medications that lower stomach acid, can decrease the absorption of B12, whereas metformin, a popular diabetes drug, can decrease levels of both B12 and folate.

Summary
Pregnancy, medical conditions, surgeries, genetics, medications, dietary restrictions, and age can all affect how your body absorbs and uses B vitamins.

Health benefits of taking B vitamins

While certain conditions make it necessary for some people to supplement with B-complex vitamins, research has shown that taking a B vitamin supplement may be helpful even for people who don’t have an increased need for these nutrients.

May reduce stress and boost mood

B-complex vitamins are often used to reduce fatigue and boost mood. Some studies suggest that B vitamins can lift your spirits and improve your cognitive performance.

Another study in healthy adults showed that supplementing with a multivitamin containing high levels of B-complex vitamins for 90 days reduced negative mood symptoms.

May reduce symptoms of anxiety or depression

While B-complex vitamin supplements are not a cure for mental health conditions, they may help improve symptoms of depression or anxiety.

A 2019 systematic review found that B vitamins may help to boost mood and brain health.

Low blood levels of certain B vitamins, including B12, B6, and folate, have been linked to an increased risk of depression, which is why it’s important to rule out nutrient deficiencies if you are experiencing symptoms of depression.

Summary
B-complex supplements may boost your mood and reduce symptoms of depression and anxiety, even in people without B vitamin deficiencies.

Recommended dosage

Each B vitamin has a specific recommended daily amount that varies depending on biological sex, age, and other factors like pregnancy.

For women and men, the recommended daily intake (RDI) for B vitamins is as follows:

Women	Men
B1 (thiamine)	1.1 mg	1.2 mg
B2 (riboflavin)	1.1 mg	1.3 mg
B3 (niacin)	14 mg	16 mg
B5 (pantothenic acid)	5 mg (RDI not established)	5 mg
B6 (pyridoxine)	1.3 mg	1.3 mg
B7 (biotin)	30 mcg	30 mcg
B9 (folate)	400 mcg	400 mcg
B12 (cobalamin)	2.4 mcg	2.4 mcg

If you are deficient in B vitamins, you may need to supplement with higher doses to address the deficiency.

For these reasons, it’s important to choose a B-complex supplement based on your individual requirements for each B vitamin.

Consider speaking with a healthcare professional about your specific nutrient needs based on your age and health.

Summary
The recommended intake for B vitamins varies depending on age, nutrient demands, biological sex, and health status.

Potential side effects

Since B vitamins are water-soluble, it’s unlikely that you will consume too much of these nutrients through food or by taking a B-complex supplement as directed.

However, taking supplements that contain excessively high and unnecessary quantities of B vitamins could lead to serious side effects.

High doses of supplemental B3 (niacin) may lead to vomiting, high blood sugar levels, skin flushing, and even liver damage.

Additionally, high doses of B6 can cause nerve damage, light sensitivity, and painful skin lesions.

Another side effect of B-complex supplements is that they can turn your urine bright yellow. Although discolored urine can be shocking, it’s not dangerous — it’s simply your body getting rid of excess vitamins that it can’t use.

If you need to take a B-complex supplement, always choose reputable brands that volunteer to have their products independently tested by organizations like the US Pharmacopeia (USP).

Summary
Although taking a vitamin B complex as directed is likely safe, consuming high doses of B3 or B6 can lead to serious side effects.

The bottom line

Pregnant people, older adults, vegans, and those with certain medical conditions may benefit from taking a B-complex supplement.

Taking these supplements may also boost mood and improve symptoms of depression.

Side effects are unlikely if you follow the recommended dosage, which varies depending on age, nutrient demands, sex, and health.

If you aren’t sure whether taking a B-complex supplement will benefit your health, consider speaking with a healthcare professional to help you determine if it’s the right choice for you.

Read this article in Spanish.

Supplements 101: Vitamin B12

How we reviewed this article:

SourcesHistoryHealthline 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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Alcohol and thiamine. (2021).https://adf.org.au/insights/alcohol-related-thiamine-deficiency/
Al Mansoori A, et al. (2021). The effects of bariatric surgery on vitamin b status and mental health.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8073305/
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Miller JW. (2018). Proton pump inhibitors, H2-receptor antagonists, metformin, and vitamin b-12 deficiency: Clinical implications.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6054240/
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Rondanelli M, et al. (2019). Micronutrients dietary supplementation advices for celiac patients on long-term gluten-free diet with good compliance: A review.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6681258/
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Turgut M, et al. (2018). Biotin and chromium histidinate improve glucose metabolism and proteins expression levels of IRS-1, PPAR-γ, and NF-κB in exercise-trained rats.https://jissn.biomedcentral.com/articles/10.1186/s12970-018-0249-4
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Medically reviewed by Cynthia Cobb, DNP, APRN, WHNP-BC, FAANP — Written by Jillian Kubala, MS, RD — Updated on June 6, 2024

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Nutrition

What are B-complex vitamins?

Who should take a vitamin B complex?

People who are pregnant or nursing

Older adults

Those with certain medical conditions

Vegetarians and vegans

People taking certain medications

Health benefits of taking B vitamins

May reduce stress and boost mood

May reduce symptoms of anxiety or depression

Recommended dosage

Potential side effects

The bottom line

Supplements 101: Vitamin B12

How we reviewed this article:

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