Methemoglobin [647X]

Test Code

CPT Codes

May include a Hemoglobin level

Preferred Specimen
5 mL whole blood collected in an EDTA (lavender-top) tube

Minimum Volume
0.5 mL

Specimen must be delivered within 72 hours of collection time for analysis.
Please note: Heparinized or citrated whole blood can also be used if client provides a hemoglobin result on the patient.

Transport Temperature
Refrigerated (cold packs)

Specimen Stability
Room temperature: 2 hours
Refrigerated: 72 hours (from collection time)
Frozen: Unacceptable


Setup Schedule
Set up: Daily a.m.; Report available: 1 day

Reference Range
<2.0 % of total Hgb

Clinical Significance
The iron in hemoglobin is normally maintained in the ferrous state by several effective mechanisms so that only a small percentage of the total hemoglobin is in the form of methemoglobin. The production of methemoglobin by oxidation of the iron to the ferric state, renders the hemoglobin incapable of interacting reversibly with molecular oxygen. The oxygen affinity of the unaffected heme is also increased, resulting in the decreased release of oxygen to the tissues at low partial pressure of oxygen.
Methemoglobinemia is usually caused by exposure to various chemical agents, many which contain nitrogen. An increase in methemoglobin can also occur due to methemoglobin reductase deficiency (congenital methemoglobinemia).

Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.