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Methemoglobin Blood Test

Last updated June 11, 2019

Approved by: Krish Tangella MD, MBA, FCAP

The Methemoglobin Blood Test helps determine the levels of methemoglobin in blood. It is used to diagnose methemoglobinemia.

What are other Names for this Test? (Equivalent Terms)

  • Hb M Blood Test
  • Hemoglobin M Blood Test

What is Methemoglobin Blood Test? (Background Information)

  • Methemoglobin (Hb M) is a dysfunctional form of the oxygen-carrying protein hemoglobin. It may result in oxygen deficiency and further complications affecting tissue function
  • Oxygen is extremely important in sustaining human life. It is so important that fully one-third of the body’s 75 trillion cells are red blood cells; the vehicles for oxygen transport
  • The so-called “bed” of these vehicles, the storage part, is hemoglobin. Each red blood cell is 97% hemoglobin, meaning that there is a tremendous amount of hemoglobin present at any one time in the body - around 0.75 kg!
  • Iron is necessary to hemoglobin because it serves essential structural and functional roles. Methemoglobin is a form of hemoglobin in which iron holds on to the hemoglobin protein in a chemical form that results in abnormal oxygen exchange. A normal oxygen exchange between the hemoglobin and the tissue is required for well-functioning of the body
  • Unlike hemoglobin, methemoglobin cannot bind oxygen effectively. Hence, methemoglobin is not a good transporter of oxygen from the lungs to the various parts of the body. This affects a variety of organs, which do not function well due to a lack of oxygen, including causing certain cardiovascular conditions
  • Methemoglobin arises due to chemicals, radiation, and drugs (such as nitrates and anesthetics), or acquired enzyme deficiencies. Infants are more prone to developing high methemoglobin levels called methemoglobinemia
  • The Methemoglobin Blood Test helps determine the levels of methemoglobin in blood. It is used to diagnose methemoglobinemia

What are the Clinical Indications for performing the Methemoglobin Blood Test?

Following are the clinical indicators for performing the Methemoglobin Blood Test:

  • Bluish skin
  • Fatigue
  • Troubled breathing
  • Dizziness
  • Headache
  • Abnormal heart rate
  • Infant born with cyanosis

How is the Specimen Collected for Methemoglobin Blood Test?

Following is the specimen collection process for Methemoglobin Blood Test:

Sample required: Blood 

Process of obtaining a blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Methemoglobin Blood Test Result?

  • A high value (greater than 20%) for the Methemoglobin Blood Test may point to a diagnosis of methemoglobinemia

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • A deficiency in the enzyme glucose-6-phosphate dehydrogenase (G-6-PD) increases production of methemoglobin

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

The following DoveMed website link is a useful resource for additional information:


Please visit our Laboratory Procedures Center for more physician-approved health information:


References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 6, 2016
Last updated: June 11, 2019