Vitamin B12 and folate tests explained

What are vitamin B12 and folate deficiency anaemia?

Vitamin B12 and folate are both needed to make healthy red blood cells. When either is lacking, the body can make abnormally large red blood cells that do not work as they should. This is called vitamin B12 or folate deficiency anaemia. Folate deficiency can affect fertility, though this is usually temporary and can be reversed with folate supplements. NHS Inform lists broccoli, Brussels sprouts, asparagus, peas, chickpeas and brown rice as examples of foods containing folate. A blood test for intrinsic factor antibodies helps diagnose pernicious anaemia.

What symptoms can it cause?

The NHS lists tiredness, muscle weakness, numbness, pins and needles, psychological problems and problems with balance and coordination. Breathlessness, headaches, palpitations and pale or yellowish skin also appear in some lists of symptoms. A Glasgow-area hospital note says nerve effects of B12 deficiency can occur without anaemia. Mouth ulcers, a sore red tongue and problems with vision or memory are also listed.

How is it diagnosed?

A GP typically combines symptoms with blood tests. The blood tests check the level of vitamin B12 and the level of folate in the blood. A UK clinical guideline notes that a vitamin B12 blood test is not completely reliable and asks for two tests when deficiency is suspected. An NHS haematology service says B12 testing should be limited to people with suspected deficiency and not used as a screening test. Guidance advises referral to a haematologist when the cause of deficiency is still uncertain after investigation.

What causes deficiency?

The NHS says pernicious anaemia is the most common cause of vitamin B12 deficiency in the UK. Pernicious anaemia is an autoimmune condition that affects the stomach, so B12 from food is not absorbed. Lack of B12 from the diet is uncommon, but it can happen with a vegan diet that includes no supplements or fortified foods. Some medicines, including proton pump inhibitors and metformin, can reduce B12 levels. The NHS notes that some medicines, including anticonvulsants, can affect how much of these vitamins the body absorbs. NHS Inform lists a diet low in folate, heavy alcohol use, malabsorption, pregnancy and some medicines as causes of folate deficiency.

How is it treated?

B12 deficiency anaemia is usually treated with injections of vitamin B12, called hydroxocobalamin. When the cause is diet, treatment may be daily B12 tablets instead. Folate deficiency is usually treated with folic acid tablets. Clinicians check B12 status first, because folic acid can mask a vitamin B12 deficiency. Follow-up blood tests check that treatment is working. A GP appointment is the route for symptoms such as numbness, pins and needles or problems with balance.