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Hemoglobin

Published: July 27, 2026Updated: August 25, 2026

Hemoglobin measures the concentration of this oxygen-carrying protein in red blood cells, crucial for assessing oxygen transport and anemia.

Quick summary

Hemoglobin levels indicate oxygen-carrying capacity and can diagnose anemia.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
g/dL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Sysmex Hemoglobin, Abbott Hemoglobin, Siemens Hemoglobin, Horiba Hemoglobin
interpretation: {"text":"Indicates anemia, which may be due to nutritional deficiencies, blood loss, or chronic diseases.","label":"Low"}; {"text":"Suggests polycythemia or conditions like COPD or heart disease, indicating increased oxygen-carrying capacity.","label":"High"}

Hemoglobin (Hb or Hgb) is a protein in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the lungs. The normal concentration of hemoglobin in the blood is typically between 12 and 17.5 grams per deciliter (g/dL) for adult males and slightly lower for females.

A low hemoglobin level is a common indicator of anemia, which can result from various conditions such as nutritional deficiencies (e.g., iron, vitamin B12, folate), chronic diseases, or blood loss. High hemoglobin levels may suggest conditions like polycythemia, chronic obstructive pulmonary disease (COPD), or heart disease.

Hemoglobin testing is a routine part of complete blood count (CBC) tests and is essential for diagnosing and monitoring conditions that affect red blood cells. It helps in evaluating the overall oxygen-carrying capacity of the blood and guides treatment strategies for patients with anemia or other related disorders.

Frequently asked questions

What is a normal hemoglobin level?
Normal hemoglobin levels for adults range from 12 to 17.5 g/dL.
What causes low hemoglobin?
Low hemoglobin can be caused by iron deficiency, vitamin B12 deficiency, chronic diseases, or blood loss.
  1. 1
    Mayo Clinic: Hemoglobin testSource
  2. 2
    American Society of Hematology: AnemiaSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

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If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy