Folate Deficiency and Megaloblastic Anemia: Causes, Signs and Who Is at Risk

See a clinician before treating yourself

Folate (vitamin B9) deficiency can cause anemia and other problems, and some of its symptoms overlap with vitamin B12 deficiency. The NHS says you should see a GP if you think you may have either, because both can be diagnosed with symptoms and blood tests. [1] This matters because folic acid can improve symptoms so much that it hides an underlying B12 deficiency that can harm the nervous system, which is why the NHS says the GP checks B12 before starting folic acid. [2] Do not start or stop supplements without that check.

Evidence labels used here: established nutritional role / deficiency treatment and Proper evidence not found.

What it is

Folate deficiency means a lower-than-normal amount of folate in the blood. MedlinePlus explains that folate is water-soluble, so it is not stored in large amounts, and blood levels can get low after only a few weeks of a low-folate diet. [3] The NHS says the body's folate store usually lasts about 4 months. [4]

In megaloblastic anemia, red blood cells are abnormally large and do not work properly. The NHS says most people with B12 or folate deficiency anaemia have underdeveloped red blood cells that are larger than normal. [4] MedlinePlus notes severe cases can also lower white blood cells and platelets. [3]

Causes and who is at risk

Never stop a prescribed medicine because it is on a list like this. If a medicine you take is listed, ask your prescriber or pharmacist whether any monitoring is advised; the NHS says your GP will be aware of these medicines and will monitor you if necessary. [4] See Vitamin and medicine interactions, Vitamins and alcohol and Malabsorption, celiac disease, IBD and vitamin deficiency.

Signs and symptoms

MedlinePlus lists fatigue, irritability, diarrhea, poor growth and a smooth, tender tongue. [3] The NHS lists a wide range shared with B12 deficiency, including tiredness, breathlessness, palpitations, headaches, a sore red tongue, mouth ulcers and problems with memory and judgment, and says some of these can happen without anaemia. [5] [1] These signs are not specific to folate. See Vitamin deficiency symptoms: what they can and cannot tell you.

Testing and treatment (clinician-led)

The NHS says blood tests check haemoglobin, the size of red blood cells, B12 and folate, and that symptoms are also taken into account because some people with symptoms seem to have normal levels while others have low levels without symptoms. [6] MedlinePlus notes that pregnant women commonly have this blood test at prenatal checkups. [3] Test details: Folate blood tests.

For treatment, the NHS says the GP usually prescribes folic acid tablets, mostly for about 4 months, longer or possibly for life if the underlying cause continues, with blood tests to check it is working. [2] This describes NHS practice, not a personal plan. A clinician decides amount and duration.

Pregnancy and children

MedlinePlus says folic acid deficiency in pregnancy can cause neural tube defects, which are birth defects of the spine and brain. [3] The NHS lists pregnancy complications and birth defects among possible complications of B12 or folate deficiency. [1] Official advice for the weeks around conception is on Folic acid and folate before and during pregnancy. For children the sources we read give no separate guidance beyond premature babies being more likely to be deficient. [4] Proper evidence not found for other child-specific advice in them.

Other cautions

Kidney, liver, surgery and cancer-treatment situations all change folate handling or medicine use: tell your care team about any supplement. See Medication interactions and Quality testing and certifications. Food sources are on Foods high in folate, and the full profile is Folate (vitamin B9).