Lab Test

Carboxyhemoglobin in Blood (HbCO)

Carbon monoxide

Test Codes




Specimen Collection Criteria

Preferred Specimen TypeOne Dark Green-top Lithium or Sodium Heparin tube. (Minimum Whole Blood: 0.5 mL)

NOTE:  Do NOT use Light Green Plasma Separator (PST) tubes.

Acceptable Specimen Type: One blood gas syringe (see Blood Gas Procedure below)*

*NOTE: Blood Gas Syringe specimens should ONLY be collected at the Dearborn, Farmington Hills, Grosse Pointe, Royal Oak, Taylor, Trenton, Troy, or Wayne Hospital Campuses. Specimens should NOT be collected at any other Beaumont Laboratory drawsite, Nursing Home, or Outreach office. 

For Blood Gas Syringe Collection ONLY: 

  • A 1 mL or 3 mL plastic syringe containing dry heparin is usually used to collect the specimen.
  • At least 1-2 mL (0.3 mL for pediatric patients) of blood is needed to ensure proper assay.
  • Arterial specimens are collected by a physician, nurse, or respiratory therapist.
  • For specimens collected by syringe, any air bubbles present in the syringe must be immediately expelled, the needle removed, and the syringe tightly capped. The syringe is rolled between the palms of the hands to ensure mixing.
    • Note: The Radiometer safePICO self-fill™ syringe has a metal ball to ensure homogeneous mixing when the syringe is rolled between the palms of the hands.
  • Characterization of oxygen enrichment, at the time of arterial puncture, is required. This may be expressed as FiO2 fractional inspired oxygen concentration provided (e.g., 0.50), FiO2% (e.g., 50%), room air, or nasal cannula flow rate in liters per minute. The FiO2 must be noted on the requisition or entered as part of the electronic order for any arterial blood gas specimens. FiO2 is not required for venous blood gas orders.
  • The specimen must be properly labeled.
  • Place on wet ice for transport. Ice and Specimen must be kept separated.
    • Suggested: Place specimen in front pocket of the biohazard bag. Place ice in zip lock section of biohazard bag.
  • The specimen must be transported immediately to the STAT Laboratory (Royal Oak) or to the Chemistry Laboratories.  

Physician Office/Draw Specimen Preparation

For Lithium or Sodium Heparin tubes ONLY:

DO NOT remove Vacutainer® stopper. Maintain whole blood specimen refrigerated (2-8°C or 36-46°F) prior to transport. (Minimum: 0.5 mL)

Preparation for Courier Transport

Transport: Whole blood specimen, refrigerated (2-8°C or 36-46°F) prior to transport. (Minimum: 0.5 mL)

Rejection Criteria

  • Specimens collected in fluoride or oxalate tubes.
  • Clotted specimens.
  • Specimens not collected and processed as indicated.

Inpatient Specimen Preparation

  • Transport Dark Green-top tubes to the Laboratory immediately.

  • If a blood gas syringe specimen was collected, transport STAT, on wet ice, to the STAT Laboratory (Royal Oak) or the Chemistry Laboratories. 

In-Lab Processing

Dark Green-top tubes: Deliver immediately to the appropriate testing station. The Laboratory should refrigerate (2–8°C or 36–46°F) the specimen if testing will be delayed.

Blood Gas Syringe specimens: Immediately analyze the whole blood, heparinized, iced specimen upon receipt.


Specimen Stability for Testing:

Dark Green-top Heparin Tubes
Room Temperature (20–26°C or 68–78.8°F): 4 hours
Refrigerated (2–8°C or 36–46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Blood Gas Syringes

Room Temperature (20–26°C or 68–78.8°F): Unacceptable
Refrigerated (2–8°C or 36–46°F): 1 hour
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Green-top tubes: Refrigerated (2–8°C or 36–46°F) for 7 days.
Blood Gas Syringes: Specimens are disposed within 8 hours of testing.


Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Lenox Main Laboratory
Livonia Main Laboratory
Royal Oak STAT Laboratory
Taylor Chemistry Laboratory
Trenton Chemistry Laboratory
Troy Chemistry Laboratory
Wayne Main Laboratory 


Sunday – Saturday, 24 hours a day.
Routine results available within 24 hours.
STAT results available within 1 hour after receipt in the Laboratory.

Reference Range

Non-smoker: Less than 1.5%.
Heavy smoker: Less than 9%.
Toxic: Greater than 20%.

Test Methodology

Absorption Spectrophotometry.


Sulfhemoglobin levels of 10% are reported to increase the HbCO reading by approximately 2.5%.

A high turbidity level corresponding to 5% of Intralipid can affect the HbCO results by +1%.

Clinical Utility

This assay aids in the diagnosis of carbon monoxide poisoning.

CO Hb (%)  Symptoms/Signs of Carbon Monoxide Poisoning
10  No appreciable effect; may have tightness across forehead.
20  Short of breath on moderate exertion; occasional headaches.
30  Headache, irritable, easily fatigued.
40-50  Headache, confusion, collapse.
60-70  Unconscious, convulsions, respiratory failure.
80+  Rapidly fatal.

Carbon monoxide combines with the heme Fe2+ of hemoglobin to form carboxyhemoglobin. The binding affinity is about 250 times greater than that of oxygen. In addition to this increased binding affinity with subsequent decreased oxygen content of blood, there is a shift of the hemoglobin oxygen dissociation curve to the left, causing a decrease in release of oxygen from hemoglobin.

CPT Codes

82375 (Quantitative), 82376 (Qualitative).
LOINC:  2030-5, 31157-1


Last Updated


Microtainer® and Vacutainer® are registered trademarks of Becton, Dickinson and Company.
UroVysion® is a registered trademark of Abbott Laboratories. ThinPrep® is a registered trademark of Hologic, Incorporated.