Unit Converter
Folate
(Vitamin B9 – Essential for DNA Synthesis, Cell Division, Pregnancy, and Hematology)
Synonyms
- Folate
- Folic acid (synthetic form)
- Vitamin B9
- Tetrahydrofolate (THF) derivatives
- RBC folate
- Serum folate
Units of Measurement
- pmol/L
- nmol/L
- ng/mL
- ng/dL
- ng/100 mL
- ng%
- ng/L
- µg/L
Key Conversions
1 ng/mL = 2.266 nmol/L (MW ≈ 441 g/mol)
1 ng/dL = 0.01 ng/mL
ng/dL = ng% = ng/100 mL
1 ng/mL = 1000 ng/L = 1 µg/L
Description
Folate is a water-soluble B-vitamin (Vitamin B9) required for:
- DNA synthesis
- Purine and pyrimidine formation
- Red blood cell (RBC) production
- Methylation reactions (with B12)
- Neural tube development in pregnancy
The body does not store folate extensively, so deficiency can develop rapidly (weeks–months).
Dietary sources include leafy vegetables, legumes, fruits, liver, and fortified grains.
Physiological Role
Folate is essential for:
- Cell division
- Bone marrow function
- Fetal neurodevelopment
- Homocysteine metabolism (via methylation)
- S-adenosylmethionine (SAMe) production
Deficiency affects rapidly dividing cells first (e.g., bone marrow, GI mucosa).
Clinical Significance
Low Folate (Folate Deficiency)
Most common and clinically important finding.
Causes
- Poor dietary intake
- Alcoholism
- Malabsorption (celiac disease, IBD)
- Medications (methotrexate, phenytoin, TMP-SMX)
- Pregnancy / increased requirements
- Hemolytic anemia (↑ cell turnover)
- Bariatric surgery
- Prematurity in infants
Symptoms
- Macrocytic anemia (MCV ↑)
- Fatigue, pallor
- Glossitis
- Diarrhea
- Elevated homocysteine
- NO neurologic features (unlike B12 deficiency)
Pregnancy Risk
Low folate in pregnancy →
Neural tube defects (NTD), including:
- Spina bifida
- Anencephaly
High Folate
Usually benign.
Possible causes:
- Supplementation
- Fortified diets
- Bacterial overgrowth
- Hemolysis (false elevation)
High folate does not mask B12 deficiency neurologically but may normalize hematologic indices.
Reference Intervals
(Tietz 8E + WHO + AACE + Mayo + ARUP)
Serum Folate
- >4 ng/mL (≈ >9 nmol/L) = normal
- 2–4 ng/mL (4.5–9 nmol/L) = borderline
- <2 ng/mL (≈ <4.5 nmol/L) = deficiency
RBC Folate
Better reflects long-term stores.
- >150 ng/mL (≈ >340 nmol/L) = normal
- <150 ng/mL = deficiency
Pregnancy Targets
- >4 ng/mL serum folate
- >150 ng/mL RBC folate
WHO Criteria
- RBC folate < 305 nmol/L → Increased NTD risk
Diagnostic Uses
1. Evaluation of Macrocytic Anemia
Differentiate folate deficiency from B12 deficiency.
2. Pregnancy Screening
Assess adequate folate to prevent neural tube defects.
3. Malabsorption Disorders
Celiac disease, Crohn’s disease, short bowel syndrome.
4. Alcohol Dependence
Alcohol interferes with folate absorption and metabolism.
5. Hyperhomocysteinemia Evaluation
Folate deficiency → ↑ Homocysteine (CV risk marker).
6. Monitoring Therapy
Assess response to folic acid supplementation.
Analytical Notes
- Serum folate reflects recent intake; RBC folate reflects long-term status.
- Hemolysis falsely increases folate (release from RBCs).
- Fasting sample preferred but not mandatory.
- Some medications reduce folate levels (antiepileptics, antifolates).
Clinical Pearls
- Folate deficiency causes macrocytic anemia without neurologic symptoms (unlike B12).
- Always check B12 along with folate.
- Pregnancy requires higher folate; supplementation reduces NTD risk by >70%.
- Borderline folate levels should not be ignored — repeat testing or treat empirically.
- Alcoholism is one of the most common causes of low folate worldwide.
Interesting Fact
Folate was discovered in spinach (Latin: folium = leaf), hence the name.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Vitamins & Nutrition.
- WHO: Serum & RBC Folate Thresholds for NTD Prevention.
- AACE/ACE Guidelines - Vitamin Deficiency Testing.
- BCSH Hematology Guidelines - Macrocytic Anemia.
- Mayo Clinic Laboratories - Folate.
- ARUP Consult - Folate & B12 Interpretation.
- MedlinePlus / NIH - Folate Test.