Guides
Low Folate (B9): Symptoms and Test Results
Low folate can cause fatigue and pallor when it leads to anemia. How to read the test value, why B12 is also checked, and when to see a doctor.
Translated from the Turkish original by DoktorClub. The Turkish version is the reference text; this English translation has not been separately reviewed by a physician. Read the Turkish original.
Key takeaway
Yes, folate deficiency can cause fatigue and pallor when it leads to anemia. Redness and soreness of the tongue, mouth ulcers and forgetfulness may also occur. According to the Turkish Society of Hematology (THD) 2025 guideline, giving folic acid alone to a person with B12 deficiency can worsen neurological findings. That is why B12 is also checked when folate is low. When interpreting the result, the laboratory reference range on your report applies.
Short Answer
Yes, folate deficiency can cause fatigue and pallor when it leads to anemia. Redness and soreness of the tongue, mouth ulcers and forgetfulness may also occur. According to the Turkish Society of Hematology (THD) 2025 guideline, giving folic acid alone to a person with B12 deficiency can worsen neurological findings. That is why B12 is also checked when folate is low. When interpreting the result, the laboratory reference range on your report applies.
How does it appear on your report?
The test may appear on reports under these names:
- Folate, folic acid, serum folate: The folate level in the blood (serum or plasma).
- Red cell folate (RBC folate): Folate inside red blood cells. Fewer laboratories run this test.
The Turkish Ministry of Health's unit standard uses µg/L for serum and red cell folate. According to the Ministry's unit procedure, the number does not change when converting from ng/mL to µg/L. In other words, 4 ng/mL and 4 µg/L are the same value.
Serum folate vs. red cell folate: Serum folate reflects intake over the last few days. Red cell folate shows long-term status. Low red cell folate suggests chronic deficiency.
The "Tahlillerim" (My Lab Tests) section of e-Nabız (Türkiye's national health record app) shows your results together with their reference values. Values outside the range are color-coded.
Reference range or decision limit? The Ministry's procedure requires decision limits to be marked with an asterisk (*) on the report. Folate is not on the Ministry's priority decision-limit list. Some laboratories may still show "deficiency" or "borderline" bands; read the footnote.
Normal value and reference range
There are differences between folate measurement methods. The values below are examples and typical thresholds.
| Test | Value | Interpretation | Source |
|---|---|---|---|
| Serum folate | Below 2 ng/mL (µg/L) | Deficiency | StatPearls 2025 |
| Serum folate | 2–4 ng/mL | Borderline | StatPearls 2025 |
| Serum folate | Above 4 ng/mL | Usually normal | StatPearls 2025 |
| Red cell folate | Low relative to the laboratory range | Chronic deficiency | StatPearls 2025 |
| Total B12 (together) | Below 180 ng/L | B12 deficiency confirmed | NICE NG239, 2024 |
| Total B12 (together) | 180–350 ng/L | Indeterminate; deficiency possible | NICE NG239, 2024 |
| Total B12 (together) | Above 350 ng/L | B12 deficiency unlikely | NICE NG239, 2024 |
A reference range covers 95% of healthy people; about 1 in 20 healthy people may fall slightly outside the range. A single borderline value is not enough for a diagnosis.
What does it mean if it is low?
Causes of low folate, from common to serious:
- Low recent folate intake: Not eating enough folate-rich foods. According to StatPearls, stores are limited and deficiency can develop in 8–16 weeks.
- Regular alcohol use: Alcohol impairs the absorption, storage and use of folate.
- Pregnancy and breastfeeding: The requirement increases.
- Medicines: Methotrexate, phenytoin, sulfasalazine and trimethoprim can affect folate use. Do not stop your medicine on your own.
- Malabsorption: Intestinal diseases such as celiac disease.
- Chronic hemolytic anemia: The requirement increases because blood cell breakdown is increased.
Symptoms: According to StatPearls, the most typical findings are pallor and fatigue. The tongue may be red, smooth and sore; mouth ulcers may accompany this. Depression, irritability, insomnia and cognitive problems may also occur. These symptoms are not specific; they also occur in many other conditions.
What does it mean if it is high?
With high serum folate, sample and supplement effects are considered first. Because serum folate reflects recent intake, mention it if you have used a supplement in the last few days. According to the Turkish Ministry of Health's 2024 guideline, hemolysis in the tube artificially raises folate. Hemolysis caused by skin disinfectant can have the same effect.
When read together
- Low folate + low B12: According to StatPearls, B12 treatment should be started before or together with folic acid. Folic acid alone can worsen the nerve damage of B12 deficiency.
- High homocysteine + normal MMA + normal B12: Suggests folate deficiency.
- High homocysteine + high MMA + low B12: Suggests B12 deficiency.
- High MCV (macrocytosis) + anemia: Megaloblastic anemia comes to mind; according to THD, both B12 and folate deficiency can cause it.
- Normal MCV: According to THD, coexisting iron deficiency or thalassemia trait can make the MCV appear normal or even low.
- Normal hemoglobin: According to NICE NG239, the absence of anemia or macrocytosis does not rule out B12 deficiency.
- High LDH + high indirect bilirubin: According to THD, this can be seen in megaloblastic anemia. See the high LDH page.
Preparing for the test
- Fasting and timing: The Turkish Biochemical Society guideline recommends 8–12 hours of fasting and a blood draw between 07:00 and 09:00 in the morning for routine tests.
- Supplements: Serum folate reflects recent intake. Tell the phlebotomy team about the vitamin supplements you use.
- Medicines: If you take methotrexate, phenytoin, sulfasalazine or trimethoprim, tell your physician.
- Hemolysis: In a hemolyzed sample, folate comes out falsely high. The laboratory may ask for a new sample.
- Pregnancy: NICE NG239 recommends active B12 as the first test for B12 in pregnancy.
Which doctor, which test?
- Family physician or Internal Medicine: Complete blood count, B12, folate and repeat testing if needed.
- Hematology: Marked anemia, low counts of more than one type of blood cell, or macrocytosis with no identified cause.
- Gastroenterology: If celiac disease or another malabsorption disorder is suspected.
- Obstetrics and Gynecology: If you are planning a pregnancy or are pregnant.
- Neurology: If there are neurological findings such as numbness, tingling or balance problems.
- Additional tests: B12 or active B12, homocysteine, methylmalonic acid (MMA), reticulocytes, LDH, bilirubin and ferritin.
In Türkiye
- Pregnancy planning: The Ministry's Antenatal Care Guideline (2018) recommends folic acid for every woman planning a pregnancy, starting at least 1 month before pregnancy. For the dose, see the folic acid dose article.
- High-risk groups: The same guideline recommends a higher dose for women taking antiepileptics and those with a history of a pregnancy with a neural tube defect. Your physician determines this dose.
- Routine pregnancy tests: Folate measurement is not among the guideline's routine blood tests; folic acid supplementation is recommended.
- Repeat-order interval: According to the Ministry's 2024 Rational Test Ordering list, in outpatient visits folate cannot be reordered without justification before 365 days have passed, and B12 before 180 days.
- B12 in infants: According to THD, the most common cause of B12 deficiency in infants in Türkiye is maternal B12 deficiency during pregnancy.
- Treatment warning: THD 2025 warns that in B12 deficiency, folic acid alone can worsen neurological findings.
When to seek emergency care?
- If fatigue is accompanied by chest pain, marked shortness of breath or fainting, call 112 (the emergency number in Türkiye).
- If there is new unsteadiness when walking, weakness in the legs or a change in consciousness, go to the emergency department the same day.
- If fever is accompanied by easy bruising or nosebleeds, seek care the same day. According to THD, white blood cells and platelets can also fall in severe megaloblastic anemia.
- If the laboratory has called you about a critical value (for example hemoglobin of 6.0 g/dL or below), contact a physician the same day.
Related tests
- Lab Test Guide: all tests
- Types of anemia: iron, B12, folic acid
- What should the folic acid dose be?
- Iron, TIBC and transferrin saturation
- High LDH
- How to read a complete blood count (CBC)
What changed? (October 2026)
- B12 interpretation bands were given according to the NICE NG239 (March 2024) guideline; the older BSH 2014 bands were not used.
- Warnings from the Turkish Society of Hematology Guideline on Red Cell Disorders, Version 1.4 (August 2025), were added.
- Hemolysis and repeat-order rules from the Turkish Ministry of Health Total Testing Process Guideline (2024) were added.
Sources
- Türk Hematoloji Derneği. Eritrosit Hastalıkları ve Hemoglobin Bozuklukları Tanı ve Tedavi Kılavuzu. Version 1.4, August 2025. https://file.thd.org.tr/file/ER%C4%B0TROS%C4%B0T-KILAVUZ-2025-.pdf (accessed October 2, 2026)
- T.C. Sağlık Bakanlığı HSGM. Doğum Öncesi Bakım Yönetim Rehberi. 2018, Publication No 925. https://platform.who.int/docs/default-source/mca-documents/policy-documents/guideline/TUR-MN-21-01-GUIDELINE-2018-tur-Antenatal-Care-Management-Guidelines.pdf (accessed October 2, 2026)
- T.C. Sağlık Bakanlığı SHGM. Tıbbi Biyokimya Toplam Test Süreci Rehberi. May 2024, Publication No 1287. https://dosyamerkez.saglik.gov.tr/Eklenti/48692/0/tibbi-biyokimya-toplam-test-sureci-rehberipdf.pdf (accessed October 2, 2026)
- T.C. Sağlık Bakanlığı SHGM. Test Ölçüm Birimleri. Version 2, 2021. https://dosyamerkez.saglik.gov.tr/Eklenti/41467/0/test-olcum-birimleri-versiyon-2-pdfpdf.pdf (accessed October 2, 2026)
- T.C. Sağlık Bakanlığı SHGM. Karar Sınırı (Eşik Değer), Kritik Değer (Panik Değer) ve Ölçüm Birimlerinin Harmonizasyonu Prosedürü. Akılcı Laboratuvar Kullanımı Projesi, current version. https://dosyamerkez.saglik.gov.tr/Eklenti/15143/0/karar-siniri-esik-deger-kriek42009846pdf.pdf (accessed October 2, 2026)
- T.C. Sağlık Bakanlığı. e-Nabız Kullanım Kılavuzu V2.1. 2025. https://enabiz.gov.tr/document/User_Manual.pdf (accessed October 2, 2026)
- Türk Biyokimya Derneği. Venöz Kan Alma (Flebotomi) Kılavuzu. 3rd revised edition, 2023. https://yonetim.citius.technology/files/kurum/kurum78/menu/veno-z-kan-alma--flebotomi---klavuzu-tr-3-baski.pdf (accessed October 2, 2026)
- NICE. Vitamin B12 deficiency in over 16s: diagnosis and management (NG239). March 6, 2024. https://www.nice.org.uk/guidance/ng239 (accessed October 2, 2026)
- Baddam S, Khan KM, Jialal I. Folic Acid Deficiency. StatPearls, updated June 25, 2025. https://www.ncbi.nlm.nih.gov/books/NBK535377/ (accessed October 2, 2026)
- CLSI. EP28-A3c: Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory. 3rd edition, 2010; reaffirmed in 2020. https://clsi.org/standards/products/method-evaluation/documents/ep28/ (accessed October 2, 2026)
Frequently asked questions
Does low folate cause fatigue?
Yes, folate deficiency can cause fatigue and pallor when it leads to anemia. However, a mildly low value does not always cause symptoms. Fatigue also has other causes, such as thyroid problems, iron deficiency and sleep problems. Your physician evaluates it together with a complete blood count and B12.
My folate showed up red in e-Nabız (Türkiye's national health record app). What should I do?
The red color shows that the value is outside the laboratory's reference range. First look at your complete blood count and B12 result. Do not start high-dose supplements on your own. Discuss the result with your family physician.
Why is B12 also checked when folate is low?
The two deficiencies cause similar anemia and can also occur together. According to THD, in B12 deficiency folic acid alone can worsen nerve damage. That is why B12 status is clarified first.
How long does it take for folate deficiency to develop?
According to StatPearls, the body's folate stores are limited. If intake falls sharply, deficiency can develop within 8–16 weeks. Pregnancy, alcohol and some medicines can also contribute to deficiency.
I'm planning a pregnancy. Is a folate test necessary?
The Turkish Ministry of Health's Antenatal Care Guideline does not require routine folate measurement. Instead, it recommends taking folic acid starting at least 1 month before pregnancy. If you have a risk factor, your physician decides on the dose and testing.
