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Test Code FOLATE SER Folate, Serum

Reporting Name

Folate, S

Useful For

Investigation of suspected folate deficiency

Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.6 mL

Collection Instructions: 

1. Fasting (8 hours)

2. Serum gel tubes should be centrifuged within 2 hours of collection.

3. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

Additional Information: Do not order on patients who have recently received methotrexate or other folic acid antagonists.

Seattle Children's Hospital Note:

Collect 1.2 mL whole blood in Red Top.

Specimen Type


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  90 days

Day(s) and Time(s) Performed

Monday through Friday; 5 a.m.-12 a.m.

Saturday; 6 a.m.-6 p.m.

Performing Laboratory

Mayo Medical Laboratories in Rochester

Method Name

Competitive-Binding Receptor Assay

Method Description

The instrument used is a Beckman Coulter DXI 800. The Access Folate assay is a competitive-binding receptor assay. A serum specimen is treated to release folate from endogenous binding proteins. After neutralization of the reaction mixture, folate-binding protein, mouse antifolate-binding protein, folic acid-alkaline phosphatase conjugate, and goat antimouse capture antibody coupled to paramagnetic particles are added to the reaction vessel. Folate in the sample competes with the folic acid-alkaline phosphatase conjugate for binding sites on a limited amount of folate-binding protein. Resulting complexes bind to the solid phase via mouse antifolate binding protein. After incubation in a reaction vessel, materials bound to the solid phase are held in a magnetic field, while unbound materials are washed away. The chemiluminescent substrate Lumi-Phos 530 is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is inversely proportional to the concentration of folate in the sample. The amount of analyte in the sample is determined from a stored, multipoint calibration curve. The assay is standardized to the World Health Organization (WHO) International Standard 03/178.(Beckman Coulter Assay Manual 2011, Beckman Coulter Inc., Fullerton, CA)

Reference Values

≥4.0 mcg/L

<4.0 mcg/L suggests folate deficiency

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
FOL Folate, S 2284-8


Result ID Test Result Name Result LOINC Value
FOL Folate, S 2284-8

Reject Due To


Mild OK; Gross reject


Mild OK; Gross OK





Special Instructions


If not ordering electronically, complete, print, and a Benign Hematology Test Request Form (T755) with the specimen (