What Do Low Folate Levels Mean, and What Causes Them?

Low folate levels mean a blood test has found less folate (vitamin B9) than the laboratory expects. Common reasons include a diet low in folate, regular heavy drinking, poor absorption from conditions such as coeliac disease, some medicines, and higher needs in pregnancy. A low result is a reason to look for the cause, not a diagnosis on its own.

Folate helps the body make healthy red blood cells. When it runs low for long enough, red blood cells can become larger than normal and work less well. This is called folate deficiency anaemia. Some people have low folate with a normal blood count, and some have symptoms before anaemia appears.

This guide is for adults looking at an existing folate result. It explains common causes and questions to ask. It cannot interpret your own result, set a target level or decide treatment. Reference ranges and units differ between laboratories, so compare your result with the range printed on your own report.

The NHS advises seeing a doctor if you think you may have a B12 or folate deficiency, and says diagnosis and treatment should happen as soon as possible because some problems caused by the condition can be permanent. Severe anaemia in adults can put strain on the heart.

Get medical advice promptly rather than waiting for a routine appointment if you notice:

• New or worsening pins and needles, numbness, or problems with balance or walking.
• Confusion, memory problems or marked changes in mood.
• Vision problems or muscle weakness.
• Severe tiredness with breathlessness, chest pain or a racing heartbeat. Chest pain or severe breathlessness needs emergency care through local services.

Symptoms are often gradual and can overlap with many other conditions. The NHS lists extreme tiredness and low energy, pins and needles, a sore red tongue and mouth ulcers, muscle weakness, vision problems, mood changes, and problems with memory, understanding and judgement. MedlinePlus also lists headache and pale skin.

Several of these symptoms, especially nerve symptoms, are also typical of vitamin B12 deficiency. The two deficiencies can look alike in a blood count, which is one reason clinicians often test both together. Our guide on B12 deficiency without anaemia explains why a normal blood count does not rule B12 out.

The NHS and MedlinePlus describe several groups of causes. More than one can apply to the same person.

• Diet: not eating enough folate-rich foods, such as green vegetables like broccoli, Brussels sprouts and peas, chickpeas and brown rice. Restrictive or weight-loss diets raise the risk. MedlinePlus also notes that overcooking food can reduce folate.
• Alcohol: regular heavy drinking is a recognised risk. Alcohol-related liver damage can also increase the folate lost in urine.
• Poor absorption: gut conditions, most often coeliac disease, can stop folate being absorbed well. The NHS lists tiredness linked to folate, B12 or iron deficiency anaemia among the possible signs of coeliac disease.
• Higher demand: the body needs more folate during pregnancy, and with some blood disorders, such as sickle cell anaemia or haemolytic anaemia, some cancers, and infection or inflammation.
• Extra losses: long-term kidney dialysis and some conditions such as heart failure can increase folate loss.

Some medicines reduce folate levels or make folate harder to absorb. Sources name classes and examples such as some anticonvulsant (anti-seizure) medicines, some anti-inflammatory and immune-suppressing medicines used for bowel and joint conditions, a cholesterol-lowering bile acid binder, and some antibiotics that act on folate.

Do not stop or change a prescribed medicine because of a folate result. Bring a full list of prescription medicines, over-the-counter products and supplements to your appointment, and ask whether any of them could be relevant. Some medicines are deliberately prescribed alongside a folate supplement, so the plan has to come from the prescriber.

Folate deficiency is usually treated with folic acid tablets, along with advice on folate-rich food. The NHS says that before folic acid is started, a GP will check vitamin B12 levels to make sure they are normal.

The reason is safety. Folic acid can improve the blood picture so well that it hides an existing B12 deficiency. If B12 deficiency is missed and left untreated, it can damage the nervous system. If your notes show a low folate result but no B12 result, ask whether B12 has been checked.

Treatment length depends on the cause. The NHS says most people take folic acid for about four months, and longer if the underlying cause continues. Your clinician will advise on the product, amount and duration. A high MCV on a blood count can be another clue to folate or B12 problems; see our guide on the high MCV blood test.

Folate matters before and in early pregnancy. The CDC explains that folic acid helps prevent neural tube defects, which are serious birth defects of the brain and spine. These form in the first few weeks of pregnancy, often before someone knows they are pregnant, so the CDC advises starting folic acid at least one month before conception and continuing during pregnancy.

If you could become pregnant and have a low folate result, mention this when you discuss the result. Ask which supplement and amount is right for you, as this is an individual decision that also depends on your health and medicines.

Bring the report with the result, unit, reference range and sample date. These questions can help you leave with a clear plan:

• How low is my folate compared with this laboratory's range, and was it a serum or red cell folate test?
• Was my vitamin B12 checked, and what did my full blood count show?
• What do you think is the most likely cause in my case: diet, alcohol, absorption, a medicine or something else?
• Should I be tested for coeliac disease or another absorption problem?
• Could any of my current medicines be lowering my folate?
• If I am planning a pregnancy, what should I do about folic acid?
• When will my folate be rechecked, and what result would change the plan?

On SameCase, patients and verified doctors share de-identified cases. Reading how others with low folate had their B12 checked, which causes were looked for and how follow-up tests were arranged can help you notice questions you had not thought of. Another person's case cannot tell you what is causing your result. Use what you read to prepare for your appointment, and rely on your own clinician for diagnosis and treatment.