What happens when someone has low hemoglobin?

If a disease or condition affects the body’s production of red blood cells, the hemoglobin levels may drop. Fewer red blood cells and lower hemoglobin levels may cause the person to develop anemia.

What is anemia?

Anemia is a blood disorder that occurs when there is not enough hemoglobin in a person's blood. When a person develops anemia, he or she is said to be "anemic." There are several different types of anemia. Some types cause only mild health problems, while others are much more severe. Each type of anemia comes from one of these factors:

  • The body cannot make enough hemoglobin.
  • The body makes hemoglobin, but the hemoglobin doesn't work right.
  • The body does not make enough red blood cells.
  • The body breaks down red blood cells too fast.

What causes anemia?

Your body uses iron to make hemoglobin. A lack of iron in the body is the most common cause of anemia. This is called iron-deficiency anemia. If you don’t get enough iron, your body cannot make hemoglobin. Factors that can lower your body's stores of iron include the following:

  • Blood loss (caused by ulcers, trauma, some cancers, and other conditions; and, in women, during monthly periods)
  • An iron-poor diet
  • An increase in the body's need for iron (in women during pregnancy)

What are the symptoms of anemia?

There are a number of symptoms that occur in all types of anemia, including:

  • Feeling tired
  • Trouble breathing
  • Dizziness
  • Headache
  • Feeling cold
  • Weakness
  • Pale skin

Last reviewed by a Cleveland Clinic medical professional on 02/02/2018.


  • National Heart, Lung, and Blood Institute. Anemia. Accessed 2/15/2018.
  • National Heart, Lung, and Blood Institute. Your Guide to Anemia. Accessed 2/15/2018.
  • American Society of Hematology. Anemia. Accessed 7/1/2020.
  • American Association for Clinical Chemistry/Lab Tests Online. Hemoglobin. Accessed 2/15/2018.

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