A low hemoglobin count is a commonly seen blood test result. Hemoglobin (Hb or Hgb) is a protein in red blood cells that carries oxygen throughout the body.
In many cases, a low hemoglobin count is only slightly lower than normal and doesn't affect how you feel. If it gets more severe and causes symptoms, your low hemoglobin count may indicate you have anemia.
A low hemoglobin count is generally defined as less than 13.5 grams of hemoglobin per deciliter (135 grams per liter) of blood for men and less than 12 grams per deciliter (120 grams per liter) for women. In children, the definition varies with age and sex. The threshold differs slightly from one medical practice to another.
A slightly low hemoglobin count isn't always a sign of illness — it may be normal for some people. Women who are pregnant commonly have low hemoglobin counts.
A low hemoglobin count can be associated with a disease or condition that causes your body to have too few red blood cells. This can occur if:
Diseases and conditions that cause your body to produce fewer red blood cells than normal include:
Diseases and conditions that cause your body to destroy red blood cells faster than they can be made include:
A low hemoglobin count can also be due to blood loss, which can occur because of:
Hemoglobin tests are given for many reasons, such as to screen for or help diagnose disease and to monitor treatment response. Some people learn that their hemoglobin is low when they go to donate blood. If you're told that you can't donate blood because of low hemoglobin, make an appointment with your doctor.
If you experience signs and symptoms of a low hemoglobin count, make an appointment with your doctor. Signs and symptoms may include:
Your doctor may recommend a complete blood count test to determine whether you have a low hemoglobin count or whether your signs and symptoms are caused by something else.
If your test reveals you have a low hemoglobin count, you will likely need more testing to determine the cause. Then your doctor can explain what this means for you.