What is a vitamin B12 blood test?

Vitamin B12 is one of the B group of vitamins. It is also known as cobalamin. It is vital for making red blood cells and for cell and tissue repair. Vitamin B12 also helps with nerve health.

Vitamin B12 and folate work together to help with cell functioning.

The vitamin B12 blood test measures the amount of vitamin B12 in your blood. Your folate level is usually tested at the same time.

Why would I need this test?

You may need this test if you have:

• symptoms that suggest a low level of Vitamin B12
• a medical condition that affects your ability to absorb Vitamin B12 from your gut

You can get Vitamin B12 from food such as:

• meat
• poultry
• seafood
• milk
• cheese
• eggs

If you don’t have enough vitamin B12 (deficiency) it can cause a type of anaemia called macrocytic anaemia. This can lead to neuropathy, a type of nerve damage that makes your hands and feet tingle or feel numb.

If you are pregnant, you may need extra folate and B vitamins to help with the growth and development of your baby.

Your doctor might do this test:

• if you have anaemia (lack of red blood cells) or an abnormal blood test
• if you have symptoms of neuropathy
• if you follow a vegan or vegetarian diet
• if there have been changes in your mental health
• if you are pregnant or breastfeeding

How should I prepare for this test

You may need to fast (avoid eating) for 6 to 8 hours before your blood test.

Understanding your results

A low vitamin B12 blood test result means your body lacks this vitamin. Low levels could be a sign of folate deficiency.

The results do not provide information about:

• what is causing your B12 or folate deficiency
• how severe it is

Discuss your blood test results with your doctor to understand what the result means for you.

Resources and support

About vitamin B12 testing

See Pathology Tests Explained for more information on vitamin B12 testing.

About blood testing

Visit healthdirect's 'Guide to blood testing' to learn more about blood tests in general, including information about:

• what happens during a blood test
• the accuracy of your results
• the cost of your blood tests