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These are two tests that measure the levels of vitamin B12 and folate in your blood. They are usually ordered if you have had an abnormal result from a Full Blood Count test that shows decreased haemoglobin levels, and/or large red blood cells or abnormal white blood cells and you have symptoms of anaemia or neuropathy – nerve damage. The tests can also be used as part of a pregnancy screen as during pregnancy a woman needs more B12 and folate to cater for the growing baby.

Why get tested?

These tests measure the concentration of folate and vitamin B12 in serum or plasma – the straw coloured liquid portion of the blood. The amount of folate inside red blood cells may also be measured. It will normally be at a higher concentration inside the cell than in the serum and measuring it can assess folate levels over a longer period.

What are vitamin B12 and folate?
B12 and folate are two vitamins that are part of the B complex group.  They cannot be produced in the body and must be supplied by the diet.
They work together with vitamin C to help the body make new red and white blood cells, repair other cells, and make DNA and RNA. Vitamin B12 is important for nerve health, while folate is necessary for cell division such as occurs in a rapidly growing baby during pregnancy.

Folate is found in leafy green vegetables, citrus fruits, dry beans and peas, liver and yeast while vitamin B12 is found in animal products such as red meat, fish, poultry, milk and eggs. Fortified cereals, breads and other grain products are now also important dietary sources of folate – identified as folic acid on nutritional labels – especially for vegans who do not consume any animal products. Since September 2009, mandatory folate fortification of flour in Australia has significantly reduced the incidence of folate deficiency. 

Since folate is stored in the body in smaller quantities than vitamin B12, it must be consumed more regularly. B12 and folate deficiencies can take months or even years to show up in adults. Infants and children show signs of deficiency more quickly because they haven’t had time to store sufficient amounts.

People at risk of deficiency 

  • The elderly. 
  • Those with a condition that prevents them from absorbing enough B12 and folate such as pernicious anaemia, coeliac disease, Crohn’s disease, ulcerative colitis, Helicobacter pylori, parasites/worms, reduced stomach acid from long-term antacid use, and previous stomach surgery such as gastric bypass. 
  • Heavy drinkers. 
  • Vegetarians and vegans. 
  • Those with long-term use of certain medications. 
  • Pregnant women who need increased amounts of B12 and folate.

When vitamin B12 and folate tests are likely to be ordered

Vitamin B12 and folate are usually performed after the results of a Full Blood Count and/or blood film show decreased haemoglobin levels and/or the presence of large red cells. A high mean cell volume (MCV) which is part of the Full Blood Count will show if the red blood cells are enlarged.

A deficiency in either vitamin B12 or folate can lead to a form of anaemia called macrocytic anaemia. This is when your body produces larger but fewer red blood cells with the result that your blood is unable to carry as much oxygen as it should. 
Another type of macrocytic anaemia called megaloblastic anaemia involves changes in the bone marrow. In this case, your test results will also show lower numbers of white blood cells, red blood cells and platelets. 

Malnutrition and malabsorption 

Testing for vitamin B12 and folate may be used to help assess your nutritional status if you have signs of malnutrition or malabsorption. This can be associated with alcoholism and the various conditions that cause malabsorption in the intestine, including:

  • Coeliac disease. 
  • Bacterial overgrowth in the stomach and intestines.
  • Reduced stomach acid production – stomach acid is necessary to separate vitamin B12 from the proteins in food.
  • Pernicious anaemia. Normally a molecule called intrinsic factor is made by cells that line the stomach. Vitamin B12 binds to intrinsic factor in the stomach, then the resulting compound is absorbed in the intestines. With pernicious anaemia, the body's immune system destroys the intrinsic factor significantly reducing the amount of vitamin B12 that can be absorbed.

Insufficient intake of B12 and folate
The human body stores several years’ supply of vitamin B12 in the liver and it is readily available in the food we eat, so a dietary deficiency of this vitamin should be rare in Australia. It may be seen sometimes with general malnutrition, and with someone who is vegan – especially if you do not consume any animal products including milk and eggs. It may also be seen in children of vegans and breast-fed infants. Since they do not have the stores that adults have, deficiencies in children and infants tend to occur earlier.

Increased loss of B12 and folate 

This can occur may with:

  • Heavy drinking or chronic alcoholism.
  • Drugs such as anti-seizure medications (e.g. phenytoin), metformin, omeprazole, and methotrexate.



When someone, especially an elderly person, exhibits mental or behavioural changes such as irritability, confusion, depression and/or paranoia, vitamin B12 and folate may be measured to help diagnose the underlying cause. This is often part of what is called a delirium screen, it happens mostly when elderly people are admitted to hospital. They may also be used when someone has physical symptoms that suggest a B12 or folate deficiency, including dizziness, weakness, fatigue, or a sore mouth or tongue. 


If you have symptoms suggesting nerve damage or impairment, such as tingling, burning, or numbness in your hands or feet, a vitamin B12 test may be requested to look for vitamin B12 deficiency.

Sometimes B12 and folate tests are ordered as part of a pre- pregnancy health screen along with a range of other tests that may help ensure a woman is in the best health for a pregnancy. During pregnancy there is a need for more B12 and folate to cater for the rapidly growing baby. If a woman has low folate at the start of pregnancy, it will become even more depleted as time goes on and may lead to premature birth or neural tube birth defects such as spina bifida.  Australian guidelines recommend women of reproductive age to consider taking folic acid supplements to reduce the risk of neural tube defects.

When a breastfed baby has a vitamin B12 or folate deficiency, the mother may also be tested to see if she has a deficiency that is affecting both her and her child.


Treatment monitoring
Sometimes, B12 and folate tests need to be repeated to see if the results change over time. This can indicate whether your condition is getting better or worse and whether any treatment you are having is working. You may need further, different tests to see what’s causing your symptoms. You can only receive a Medicare rebate for a vitamin B12 serum test once every 12 months, in line with current best practice.

Having the test


Test preparation?  
Fasting for six to eight hours before sample collection may be required especially for serum folate testing. Biotin found in some supplements can interfere with testing. Certain medicines can affect the test results. Your doctor will advise you on what to stop taking. Ask for specific instructions. 

Your results

Reading your test report

Your results will be presented along with those of your other tests on the same form.  You will see separate columns or lines for each of these tests. 

Normal B12 and folate levelsThis may mean that you do not have a deficiency and that your symptoms are due to another cause. However, normal levels may reflect the fact that your stored B12 and/or folate have not yet been fully depleted.
If you have a normal or low-normal B12 result but a deficiency is still suspected,

Your doctor may order a methylmalonic acid (MMA) test which is an early indicator of B12 deficiency.

B12 and folate tests cannot tell you the severity of a deficiency or the cause.

Low B12 and/or folate levelsThis means that you have a deficiency and further tests need to be done to investigate the underlying cause.
High levels of B12This is uncommon and not usually clinically monitored. Someone with chronic myeloproliferative neoplasm, diabetes, heart failure, obesity, AIDS, or severe liver disase, may have an increased vitamin B12 level. Taking oestrogens, vitamin C or vitamin A can also cause high B12 levels.

Any more to know?

It is possible to have low B12 or folate levels on blood tests without any clinical problems. 

In the case of B12 measurements, this partly reflects a weakness in the standard B12 blood test (also called serum cobalamin) which does not directly measure whether there is an actual deficiency of active vitamin B12 in the cells of the body.

Second-line tests that might help determine true deficiency include plasma/urine methylmalonic acid and plasma homocysteine. Serum holotranscobalamin –  is a biological active form of vitamin B12.  Testing for holotranscobalamin and B12 can be used to diagnose and monitor vitamin B12 deficiency. 

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

Get further trustworthy health information and advice from healthdirect.

Last Updated: Thursday, 1st June 2023

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