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Vitamin B deficiency

5-minute read

Key facts

  • Vitamin B deficiency happens when your body doesn’t have enough vitamin B.
  • Your body needs a certain amount of each type of vitamin B to function well.
  • Vitamin B deficiency can cause diseases such as beriberi, pellagra or anaemia.
  • People who are vitamin B deficient may feel tired, numbness or weak, among other symptoms.

What is vitamin B deficiency?

Vitamin B deficiency happens when your body doesn’t have enough vitamin B. This happens if you don’t eat food with vitamin B or because of a health condition. Your body needs a certain amount of each type of vitamin B to function well. The different types of vitamin B are all water-soluble (dissolves in water), which means that they cannot be stored in the body and must be consumed regularly to avoid deficiency.

Every day, the average adult needs:

  • 1.1-1.2mg of thiamine (B1)
  • 1.1-1.6mg of riboflavin (B2)
  • 14-16mg of niacin (B3)
  • 4-6mg of pantothenic acid (B5)
  • 1.3-1.7mg of pyridoxine (B6)
  • 25-30µg (micrograms) of biotin (B7)
  • 400µg of folate (B9)
  • 2.4µg of cyanocobalamin (B12)

Go here for information on foods high in vitamin B, or here for information on vitamin B and your health, including supplements.

What are the symptoms of vitamin B deficiency?

People with vitamin B deficiency may experience:

  • fatigue, weakness or a general lack of energy
  • numbness or tingling in their hands and feet
  • weakened muscles and slow reflexes
  • ‘shakiness’ when walking or difficulty keeping balance

More severe symptoms include confusion, a loss of memory, depression and dementia.

Am I at risk of vitamin B deficiency?

You may be at risk of vitamin B deficiency if you don’t include vitamin B in your diet or if you are malnourished.

Changes to your gastrointestinal tract (due to surgery in your abdomen or disease in your gastrointestinal tract) can also put you at greater risk of vitamin B deficiency. This happens because changes to your gastrointestinal tract can make it harder to absorb vitamins from foods and drinks.

Vitamin B deficiency can also be caused by alcoholism, since the liver needs more vitamin B to metabolise (break down) the excess alcohol.

The Australian Dietary Guidelines recommend people with a vegan diet to take a B12 supplement. Deficiency is more common in this group of people.

In some cases, deficiency in one type of vitamin B can cause a deficiency of another type because they rely on each other to function properly.

If you think you might be at risk of vitamin B deficiency, speak with your doctor or an accredited dietician. Ask for nutrition advice and whether you need a supplement.

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What are the impacts of vitamin B deficiency?

Symptoms of vitamin B deficiency differ, depending on which type of vitamin B you don’t have enough of. However, symptoms are usually mild and can be treated by having more food rich in B vitamins. In more severe cases, vitamin B deficiency can have more serious consequences. For example, a deficiency in B1 can cause beriberi disease. This can affect the cardiovascular system or the nervous system. A B3 deficiency can cause pellagra, a disease that mainly affects the skin but can also cause dementia. B12 deficiency can cause anaemia and neurological damage.

If you are planning pregnancy, you should take a vitamin B9 (folate) supplement at least 1 month before conception and for the first trimester of pregnancy to help prevent foetal neural tube defects.

What happens if I have too much vitamin B?

Vitamin B12, like other B-group vitamins, is water-soluble. This means that in most cases, the extra vitamin B in your body will pass naturally out of your body. However, overdose poisoning can occur. For example, if you take too much B6, it can result in nerve damage.

If you are concerned that you have taken too much of a vitamin B supplement, call the Poisons Information Centre (13 11 26) immediately.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: May 2022

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