Hemoglobin: Function, test, normal levels

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells (erythrocytes). Hemoglobin in blood carries oxygen from the lungs to the rest of the body. A healthy individual has 12 to 20 grams of hemoglobin in every 100 ml of blood.

Hemoglobin levels are measured by blood tests. Hemoglobin, or Hb, is usually expressed in grams per deciliter (g/dL) of blood. As hemoglobin carries oxygen in the body, a low level of hemoglobin in the blood will directly cause a low level of oxygen.

The normal ranges of hemoglobin in the blood are:

  • Newborns: 17 to 22 g/dL
  • One (1) week of age: 15 to 20 g/dL
  • One (1) month of age: 11 to 15 g/dL
  • Children: 11 to 13 g/dL
  • Adult males: 13.5 to 17.5 g/dL
  • Adult women: 12.0 to 15.5 g/dL

All of these values may vary slightly between laboratories.

Lower than normal results

A lower-than-normal hemoglobin value suggests you have anemia. There are many forms of anemia from different causes:

  • Iron deficiency
  • Vitamin B-12 deficiency
  • Folate deficiency
  • Bleeding
  • Cancers that affect the bone marrow, such as leukemia
  • Kidney disease
  • Liver disease
  • Hypothyroidism
  • Thalassemia — a genetic disorder that causes low levels of hemoglobin and red blood cells

Higher than normal results

Conditions that may lead to a higher-than-normal hemoglobin value include:

  • Polycythemia vera — a blood disorder in which your bone marrow makes too many red blood cells
  • Lung disease
  • Dehydration
  • Living at a high altitude
  • Heavy smoking
  • Burns
  • Excessive vomiting
  • Extreme physical exercise
* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.