Sign in →

Test Code MTHX Methotrexate, Serum

Useful For

Determining whether methotrexate is being cleared appropriately and verifying that a nontoxic concentration has been attained following therapy

Method Name


Reporting Name

Methotrexate, S

Specimen Type


Ordering Guidance

For patients that have received glucarpidase (carboxypeptidase G2) as a high-dose methotrexate rescue therapy, order MTXSG / Methotrexate Post Glucarpidase, Serum.

Shipping Instructions

Ship specimen in amber vial to protect from light.

Specimen Required

Supplies: Sarstedt 5 mL Aliquot Tube (Amber) (T915)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Amber vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Methotrexate is sensitive to fluorescent light; avoid prolonged exposure of specimen to direct light.

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

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

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days LIGHT PROTECTED
  Frozen  28 days LIGHT PROTECTED
  Ambient  72 hours LIGHT PROTECTED

Reference Values

Nontoxic drug concentration after 72 hours: <0.1 mcmol/L

Report Available

Same day/1 day

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US 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
MTHX Methotrexate, S 14836-1


Result ID Test Result Name Result LOINC Value
MTHX Methotrexate, S 14836-1

Day(s) Performed

Monday through Sunday


If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.