Specimen Information

Type

***CALL LAB FOR INSTRUCTIONS AND SUPPLIES***
Two (2) Green top (heparin) tubes, AND
Two (2) special collection tubes containing 40 mg oxalic acid

Volume

4.0 mL oxalic acid-preserved plasma

Transport Info

CRITICAL FROZEN – Separate samples must be submitted when multiple tests are ordered
The oxalic acid preservative may interfere with other tests
Promptly centrifuge 15 minutes
Immediately transfer 2.0 mL plasma to each of 2 separate plastic collection tubes containing 40.0 mg oxalic acid
Mix and freeze
Adequate preservation is 20 mg oxalic acid to 1 mL plasma

Fasting Required?

False

Clinical Significance

Vitamin C concentrations between 0.2-0.4 mg/dL indicate risk of deficiency. Concentrations less than 0.2 mg/dL are consistent with deficiency.

L-ascorbic acid (vitamin C) is a cofactor for protocollagen hydroxylase, the enzyme necessary for the formation of collagen and other connective tissue proteins. It also facilitates the absorption of dietary iron and is involved in a number of other metabolic pathways. Prolonged vitamin C deficiency results in scurvy, which is confirmed by concentrations of less than 0.1-0.2 mg/dL. Vitamin C concentrations of 0.2-0.4 mg/dL indicate a risk of deficiency. Iron deficiency anemia and/or folate deficiency may also be present. Concentrations less than 0.2 mg/dL are consistent with deficiency. Excessive ("megadose") vitamin C intake is generally believed to be non-toxic, but may lead to nephrolithiasis (calcium oxalate), uricosuria, and increased iron absorption.