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Vitamin B complex is used to increase the levels of various B vitamins in the body. The specific ingredients in vitamin B complex vary by product. Vitamin B complex is usually well tolerated, but it may have different side effects depending on the ingredients in the product. Before taking vitamin B complex, tell your health care provider about all of your health conditions and any medicines or supplements you may be using. 

Uses

What is vitamin B complex used for?

Vitamin B complex is commonly used to prevent or treat low levels of B vitamins.

There are a variety of vitamin B complex products available. These products may contain other ingredients, such as other vitamins, minerals, or other supplements. The components of vitamin B complex can also be found in many multivitamins. Check the label of your product closely and ask your health care provider if you have any questions.

Note: The Food and Drug Administration (FDA) has not reviewed vitamin B complex for safety and effectiveness, and it is not FDA-approved. Learn more about dietary supplements here.

How does vitamin B complex work (mechanism of action)?

B vitamins are a group of vitamins that have important functions in the body. Many of these vitamins help your body create energy. They are also important for the growth and function of your cells. All of these vitamins are water-soluble, which means that your body usually flushes out any extra B vitamins that it does not need. Most people get enough B vitamins from their diet.

There are eight B vitamins that are commonly found in vitamin B complex products.

While some vitamin B complex products contain all of these B vitamins, others contain only a few of these vitamins. Vitamin B complex products may also contain other ingredients, such as vitamin C, other vitamins, and minerals.

Vitamin B complex products can help increase the levels of various B vitamins in the body. These products may also be used for other reasons, such as increasing energy levels, but their benefits for these uses are not well defined.

How should I store vitamin B complex?

Vitamin B complex products should be stored according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and away from direct sunlight. If you are not sure how to store your product, ask your pharmacist.

Side Effects

What are the most common side effects of vitamin B complex?

Vitamin B complex is usually well tolerated. But the ingredients in vitamin B complex vary by product, which may change the risk of side effects. Tell your health care provider if you have any side effects that bother you.

There may be side effects of vitamin B complex that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of vitamin B complex?

While less common, the most serious side effects of vitamin B complex are described below, along with what to do if they happen.

Severe Allergic Reactions. Vitamin B complex may cause allergic reactions, which can be serious. Stop taking vitamin B complex and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use vitamin B complex?

Allergies to Ingredients. People who are allergic to any of the following should not take vitamin B complex.

  • B-complex
  • Vitamin B complex
  • Any other product known as a B vitamin
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific vitamin B complex products they stock.

What should I know about vitamin B complex before using it?

There are multiple forms of vitamin B complex available, which may have different ingredients or be taken in various ways. Most forms of vitamin B complex are available over the counter as a dietary supplement. These products cannot be marketed to treat or cure a disease. If you are taking one of these products, read and follow the instructions that come with the product or take it as your health care provider recommends. If you are not sure which vitamin B complex product to take, talk to your health care provider. 

Keep vitamin B complex out of the reach of children.

The FDA has not tested vitamin B complex dietary supplement products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

Vitamin B complex may also be available as a prescription that is given as an injection by a health care provider in a health care facility.

What should I tell my health care provider before using vitamin B complex?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if vitamin B complex is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have or have had any of the following.

Other Medicines and Supplements. Vitamin B complex may interact with other medicines and supplements. Before taking vitamin B complex, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Ingredients in vitamin B complex can vary by product. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will let you know if you should take vitamin B complex while you are pregnant or trying to get pregnant.

Breastfeeding. Ingredients in vitamin B complex can vary by product. Some of these ingredients pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should take vitamin B complex while breastfeeding.

Interactions

Does vitamin B complex interact with foods or drinks?

There are no known interactions between vitamin B complex and foods or drinks.

It is unknown if drinking alcohol will affect vitamin B complex, but drinking large amounts of alcohol may lower the levels of some B vitamins in your body. It is best to limit the amount of alcohol you drink.

Does vitamin B complex interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

Ingredients in vitamin B complex can vary by product. Some of these ingredients may interact with medicines. Some medicines may lower the levels of certain B vitamins in your body. 

The interactions between vitamin B complex and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with vitamin B complex is incomplete. Always check with your health care provider before taking vitamin B complex with any medicines.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much vitamin B complex?

If you or someone else has used too much vitamin B complex, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

There is a variety of vitamin B complex products available. These products may contain other ingredients, such as other vitamins, minerals, or supplements. Read the product label closely and speak with a health care provider about how to take vitamin B complex safely. Do not take double or extra doses, even if you miss a dose.