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Test Code CarnFreTo Carnitine Free and Total, blood

Clinical System Name

Carnitine Free and Total, Blood


Measurement of free, acylcarnitine and total carnitine by ESI-MS/MS using stable isotope internal standards



Sample Requirements

Specimen: Whole Blood

Container(s): Dark Green/Sodium Heparin, Lt. Green/ Lithium Heparin, Gold SST, Red

Preferred Vol: 1.0 mL

Minimum Vol: 0.5 mL


Note: Serum is also an acceptable sample type.

Processing Instructions

Reject due to:

Spin: Y

Aliquot: Y

Temp: -20 C

Storage location: -20 C Biochemical Genetics Box


Off-site collection: Freeze and ship heparinized plasma or serum. 


Temperature Time
Room temp 5 days
Refrigerated 5 days
Frozen (-200C) (serum/plasma) 1 month



STAT Performed TAT
N T, Th 3-7 days


Contact the Biochemical Genetics Lab for requests outside of stated availability (206)987-2216.

Performing Laboratory

Seattle Children's Laboratory    


Department:  Biochemical Genetics

Phone Number: 206-987-2216




Method: Tandem mass spectrometry

Analytical Volume: 0.2 mL


CPT Codes




Biochemical Genetics Requisition


On the requisition include clinical information needed for appropriate interpretation.  (Age, gender, drug therapy, and family history)

Clinical Utility

Carnitine is quantitated for the purpose of follow-up in patients with organic acidurias or fatty acid oxidation disorders who may become carnitine deficient, those on valproate or other drugs that bind to and deplete carnitine, those on hyperalimentation or dialysis, and those on supplemental carnitine.

Reference Ranges

mcmol/L < 1 wk 1 wk - 1 mo > 1 mo
Total Carnitine 17 - 41 20 - 59 29 - 84
Free Carnitine 10 - 33 16 - 57 18 - 65
Acylcarnitine 3 - 24 4 - 24 4 - 28
Acyl/Free ratio 0.2 - 1.4 0.2 - 0.5 0.1 - 0.8