Skip to main content

Complications - Vitamin B12 or folate deficiency anaemia

As most cases of vitamin B12 deficiency or folate deficiency can be easily and effectively treated, complications are rare.

But complications can occasionally develop, particularly if you have been deficient in either vitamin for some time.

Anaemia complications

All types of anaemia, regardless of the cause, can lead to heart and lung complications as the heart struggles to pump oxygen to the vital organs.

Adults with severe anaemia are at risk of developing:

  • an abnormally fast heartbeat (tachycardia)
  • heart failure, where the heart fails to pump enough blood around the body at the right pressure

Complications of vitamin B12 deficiency

A lack of vitamin B12 (with or without anaemia) can cause complications.

Neurological changes

A lack of vitamin B12 can cause neurological problems, which affect your nervous system, such as:

If neurological problems do develop, they may be irreversible.


Vitamin B12 deficiency can sometimes lead to temporary infertility, an inability to conceive.

This usually improves with appropriate vitamin B12 treatment.

Stomach cancer

If you have a vitamin B12 deficiency caused by pernicious anaemia, a condition where your immune system attacks healthy cells in your stomach, your risk of developing stomach cancer is increased.

Neural tube defects

If you're pregnant, not having enough vitamin B12 can increase the risk of your baby developing a serious birth defect known as a neural tube defect.

The neural tube is a narrow channel that eventually forms the brain and spinal cord. 

Examples of neural tube defects include:

  • spina bifida – where the baby's spine does not develop properly
  • anencephaly – where a baby is born without parts of the brain and skull
  • encephalocele – where a membrane or skin-covered sac containing part of the brain pushes out of a hole in the skull

Find out how you can reduce the risk of your baby developing a neural tube defect

Complications of folate deficiency

A lack of folate (with or without anaemia) can also cause complications.


As with a lack of vitamin B12, a folate deficiency can also affect your fertility.

But this is only temporary and can usually be reversed with folate supplements.

Cardiovascular disease

Research has shown a lack of folate in your body may increase your risk of cardiovascular disease (CVD)

CVD is a general term that describes a disease of the heart or blood vessels, such as coronary heart disease.


Research has shown that folate deficiency can increase your risk of some cancers, such as colon cancer.

Problems in childbirth

A lack of folate during pregnancy may increase the risk of the baby being born prematurely (before the 37th week of pregnancy) or having a low birth weight.

The risk of placental abruption may also be increased. This is a serious condition where the placenta starts to come away from the inside of the womb wall, causing tummy (abdominal) pain and bleeding from the vagina.

Neural tube defects and folic acid

As with a vitamin B12 deficiency, a lack of folate can also affect an unborn baby's growth and development in the womb (uterus).

This increases the risk of neural tube defects, such as spina bifida, developing in the unborn baby.

It's recommended that all women who could get pregnant should take a daily supplement of folic acid.

You should take a 400 microgram supplement of folic acid every day before you get pregnant, and up until you're 12 weeks pregnant.

Page last reviewed: 23 May 2019
Next review due: 23 May 2022