Low Folate on Your Blood Test
What low serum or red cell folate means, the causes behind it, and why checking B12 first is a critical safety step — in plain English.
The Quick Answer
Folate (also called vitamin B9 or folic acid in its synthetic form) is a water-soluble B-vitamin that your body cannot store in large amounts. It is essential for DNA synthesis, cell division, and red blood cell production. Without enough folate, your bone marrow cannot divide properly, producing fewer but larger red cells — a condition called megaloblastic anaemia.
In Australia, the most common causes of low folate are poor diet low in leafy greens and legumes, regular alcohol use, pregnancy or breastfeeding, and malabsorption from coeliac disease. Certain medications — particularly methotrexate and phenytoin — are also important causes. The good news: folate deficiency is almost always correctable with the right treatment and dietary changes.
What Does Folate Actually Do?
Folate's primary job is to carry and donate single-carbon units in a series of biochemical reactions critical to life. Most importantly, folate enables the synthesis of thymidine — one of the four building blocks of DNA. Without adequate folate, cells that divide rapidly (red blood cell precursors, the gut lining, and developing foetal tissue) are the first to suffer.
Folate also works alongside vitamin B12 in the methionine cycle, which converts homocysteine to methionine. When either B12 or folate is deficient, homocysteine builds up in the blood — a marker associated with increased cardiovascular risk. This interdependency between folate and B12 is why both must always be assessed together.
Unlike vitamin B12, folate is not stored in large amounts — total body stores are only enough for 3-4 months. This means deficiency can develop relatively quickly when intake drops or demand rises (as in pregnancy), and tends to develop faster than B12 deficiency, which can take years to deplete stores.
Causes of Low Folate
Folate deficiency usually has one or more identifiable causes. Dietary inadequacy and alcohol are the most common in Australia; medications, malabsorption, and increased physiological demand account for most other cases.
Poor dietary intake
Diets low in leafy greens, legumes, and fortified cereals. Heat destroys folate — heavily cooked vegetables lose 50–80% of their folate content. Common in elderly people, those with restricted diets, and low-income households.
Regular alcohol use
Alcohol reduces folate absorption from the gut, increases urinary losses, and disrupts folate metabolism in the liver. Even moderate regular drinking (4-5 drinks per day) can deplete folate over weeks. The combination of poor diet and alcohol is especially common.
Pregnancy and breastfeeding
Folate requirements double in pregnancy due to rapid cell division in the developing baby. Deficiency in early pregnancy raises the risk of neural tube defects (spina bifida). All pregnant women and those planning pregnancy should supplement with folic acid.
Coeliac disease
Untreated coeliac disease causes widespread malabsorption across the small intestine. Folate deficiency is one of the most common presentations of undiagnosed coeliac disease in Australian adults. A gluten-free diet typically corrects levels within months.
Inflammatory bowel disease
Active Crohn's disease involving the small bowel and severe ulcerative colitis both impair folate absorption. The inflammation reduces absorptive surface area and may increase folate losses.
Methotrexate
Methotrexate directly inhibits dihydrofolate reductase — the enzyme that activates folate. Used in rheumatoid arthritis, psoriasis, and some cancers. Patients on methotrexate routinely take weekly folic acid to reduce side effects without losing efficacy.
Phenytoin and other anticonvulsants
Phenytoin, carbamazepine, and valproate all impair folate absorption or increase folate turnover. Epilepsy patients on long-term anticonvulsants should have regular folate monitoring.
Trimethoprim and co-trimoxazole
Trimethoprim (used for urinary tract infections) and co-trimoxazole inhibit folate metabolism similarly to methotrexate. Usually only clinically significant with prolonged use or pre-existing borderline levels.
Haemolytic anaemia
Conditions that destroy red blood cells rapidly (haemolytic anaemia, sickle cell disease, hereditary spherocytosis) massively increase folate demand because the bone marrow must replace cells at many times the normal rate.
Haemodialysis
Folate is a small, water-soluble molecule lost from the blood during dialysis sessions. People on regular haemodialysis often require routine folate supplementation.
Symptoms of Folate Deficiency
Many people with mildly low folate feel entirely well. Symptoms become more noticeable when levels are significantly low or when macrocytic anaemia develops. Unlike B12 deficiency, folate deficiency alone does not cause nerve damage — but it does raise homocysteine, which has cardiovascular and cognitive implications over time.
Fatigue and weakness
The most common symptom, caused by macrocytic anaemia — the bone marrow produces fewer, larger red cells that carry oxygen less efficiently. Often described as an exhaustion that does not improve with sleep.
Shortness of breath on exertion
Reduced oxygen-carrying capacity means everyday activities like climbing stairs, walking uphill, or carrying shopping can leave you breathless. Worsens as anaemia becomes more severe.
Pallor (pale skin and lips)
Visible paleness inside the lower eyelids, in the nail beds, and on the palms. Best assessed in daylight. A useful clinical sign your GP will look for during examination.
Sore, smooth tongue (glossitis)
The tongue becomes painful, shiny, and loses its normal texture (papillae). Eating hot or spicy foods becomes uncomfortable. Classic but often overlooked in mild deficiency.
Mouth ulcers and angular cheilitis
Recurrent ulcers inside the mouth and cracking at the corners of the lips are particularly associated with folate deficiency. Often dismissed as stress-related without checking folate levels.
Low mood and irritability
Folate plays a key role in the synthesis of serotonin and dopamine. Deficiency is associated with depression, anxiety, and poor response to antidepressants. Some psychiatrists routinely check folate in patients who do not respond to treatment.
Poor concentration and mental fog
Brain function depends on adequate folate for neurotransmitter production and DNA repair. Difficulty concentrating, brain fog, and slowed thinking can all be early signs.
Palpitations and rapid heartbeat
The heart beats faster to compensate for reduced oxygen delivery when anaemia is moderate to severe. If you notice your heart racing at rest or with minimal activity, tell your GP.
Red Flags — When to See Your GP Promptly
Most people with mildly low folate can wait for their next routine GP appointment. The following situations warrant a prompt phone call:
Low folate in early pregnancy or pre-conception
Neural tube defects form in the first 4 weeks of pregnancy, before most women know they are pregnant. Confirmed folate deficiency in a woman planning pregnancy is an urgent indication for high-dose supplementation (usually 5 mg daily) and dietary counselling.
Low folate PLUS low B12
When both are deficient, B12 must be corrected first (or simultaneously) to prevent ongoing nerve damage while the blood count normalises. Do not treat folate alone until B12 is adequately replaced. This combination needs prompt GP review.
Pancytopenia (low red cells, white cells, AND platelets)
When all three cell lines are affected, severe megaloblastic anaemia or a bone marrow disorder is the likely cause. This is a medical emergency if the counts are very low. Seek urgent review.
Neurological symptoms alongside low folate
Tingling, numbness, balance problems, or memory issues suggest B12 deficiency may be co-existing. Even if your B12 appears "normal" in the lab range, neurological symptoms need prompt investigation — serum B12 can be falsely normal despite tissue deficiency.
Folate deficiency not responding to supplementation
If levels remain low after 4–8 weeks of standard folic acid 5 mg daily, malabsorption should be investigated (coeliac disease, small bowel disorder). This should not be assumed to be "poor compliance" without testing.
Raised homocysteine with normal folate and B12
A raised homocysteine despite seemingly adequate B12 and folate can indicate MTHFR gene variants, B6 deficiency, or renal impairment. Warrants further GP or specialist investigation, particularly if there is a personal or family history of blood clots or cardiovascular disease.
What Your GP Will Do Next — The Workup
Australian GPs follow a structured approach when investigating low folate. Understanding the sequence helps you know why each test is being ordered and what comes next.
Serum folate — the first-line test
Serum folate measures the amount of folate circulating in your blood right now. It is sensitive to recent dietary changes — even a few days of eating leafy greens can normalise a borderline result. Australian labs typically report normal as 7–45 nmol/L. A result below 7 nmol/L confirms deficiency.
Red cell folate — the tissue store test
Red cell folate reflects average body stores over the past 2-3 months (the lifetime of a red blood cell). It is less affected by recent diet changes and is the more reliable measure when serum folate is borderline. Normal is above 360 nmol/L. Low red cell folate with normal serum folate means stores are depleted but intake has recently improved.
Vitamin B12 — always check this first
Before treating folate deficiency, your GP must confirm your B12 level is adequate. Treating folate without checking B12 risks masking B12 deficiency, which can cause permanent nerve damage. This is one of the most important safety rules in haematology. Expect your GP to order both tests simultaneously or to insist on a B12 result before prescribing folic acid.
Full blood count and blood film
The FBC will show whether macrocytic anaemia has developed (low haemoglobin, high MCV, low red cell count). A blood film may show hypersegmented neutrophils — a classic sign of megaloblastic change from folate or B12 deficiency. The reticulocyte count may be low, indicating bone marrow is not keeping up with red cell replacement.
Homocysteine
Elevated plasma homocysteine is sensitive indicator of folate (and B12) deficiency — it rises before the blood count becomes abnormal. Some GPs use it to confirm functional deficiency when folate levels are borderline. An elevated homocysteine with low-normal folate and B12 strongly supports treatment.
Coeliac serology (if malabsorption is suspected)
If there is no obvious dietary or alcohol explanation for folate deficiency, your GP may test for coeliac disease using tissue transglutaminase antibodies (tTG-IgA). Coeliac disease is under-diagnosed in Australia — up to 80% of cases are undetected. Important to test while still eating gluten.
Review medications and alcohol
A careful review of all medications (including over-the-counter) and honest discussion of alcohol intake will often reveal the cause without further investigation. Your GP needs to know about all supplements, herbal medicines, and alcohol to interpret your results accurately.
Treatment of Folate Deficiency
Standard treatment: folic acid 5 mg daily
The first-line treatment for confirmed folate deficiency is oral folic acid 5 mg once daily (prescription strength — this is 10-12 times the dose in over-the-counter pregnancy supplements). Treatment is usually continued for 4 months, or until the underlying cause is corrected. A repeat blood test confirms that levels have normalised. Most people notice improvement in energy within a few weeks as anaemia begins to resolve.
Treating the underlying cause
Supplementation alone is not enough if the underlying cause is not addressed. For alcohol-related deficiency, reducing intake and improving nutrition are essential. For coeliac disease, a strict gluten-free diet will restore absorptive capacity. For medication-induced deficiency (methotrexate), your specialist will advise on the appropriate supplementation regime — this is usually low-dose weekly folate timed away from the methotrexate dose to preserve its therapeutic effect.
Pregnancy and periconceptional supplementation
Women planning pregnancy should take 400–800 mcg of folic acid daily starting at least one month before conception and continuing through the first trimester. Women with a previous pregnancy affected by a neural tube defect, women with coeliac disease, epilepsy on anticonvulsants, or those taking methotrexate need 5 mg daily (on prescription). This is one of the most evidence-based preventive interventions in obstetric medicine.
Monitoring response
Folate levels typically normalise within 4–8 weeks of supplementation. The MCV (mean corpuscular volume) — which may have been elevated in macrocytic anaemia — begins to fall within 1–2 weeks and usually returns to normal within 2–3 months. Haemoglobin improves more slowly, typically over 6–8 weeks. A repeat FBC and folate level after 4 months confirms response to treatment.
Best Food Sources of Folate
For most adults, diet can maintain adequate folate once levels are corrected with supplementation. The Australian Nutrient Reference Values recommend approximately 400 mcg of dietary folate equivalents (DFE) daily for adults (600 mcg in pregnancy). Note: heat destroys folate — lightly steaming or eating raw is much better than boiling.
Cooked spinach (1 cup)
Folate: ~263 mcgOne of the richest folate sources available. The word "folate" comes from "folium" (Latin for leaf). Lightly steaming rather than boiling preserves more folate.
Cooked lentils (1 cup)
Folate: ~358 mcgThe best plant-based source of folate per serve. Also high in iron and protein. Red, green, and brown lentils are all excellent choices.
Cooked chickpeas (1 cup)
Folate: ~282 mcgEasy to add to salads, curries, or eat as hummus. A staple in Middle Eastern cooking that is one of the most folate-dense everyday foods.
Asparagus (6 spears)
Folate: ~134 mcgA concentrated folate source. Best eaten lightly steamed or roasted rather than boiled. Also contains vitamin K and chromium.
Brussels sprouts (1 cup)
Folate: ~94 mcgOften underrated as a folate source. Roasting rather than boiling preserves more nutrients and makes them more palatable.
Avocado (half)
Folate: ~82 mcgA popular Australian food that is a useful folate source, especially for those who don't like leafy vegetables. Also rich in healthy monounsaturated fats and potassium.
Fortified bread and cereals
Folate: ~120 mcg per serveIn Australia, white and wholemeal wheat flour is fortified with folic acid. This is an important public health measure that contributes meaningfully to the population's daily folate intake.
Broccoli (1 cup steamed)
Folate: ~104 mcgA practical everyday vegetable with good folate content. Steam rather than boil, and eat while still slightly firm to preserve water-soluble nutrients.
Related Reading
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This page provides general educational information about folate deficiency. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your GP about abnormal blood test results — they have access to your full medical history and can interpret your results in context. SmarterBlood does not provide medical care.