Definition of low hemoglobin count
Hemoglobin (Hb or Hgb) is the protein in your red blood cells that carries oxygen. A low hemoglobin count is a below-average concentration of the oxygen-carrying hemoglobin proteins in your blood.
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 between medical practices.
A low hemoglobin count is a commonly seen blood test result. In many cases, a low hemoglobin count is only slightly lower than normal, isn’t considered significant and causes no symptoms. A low hemoglobin count can also be caused by an abnormality or disease. In these situations, a low hemoglobin count is referred to as anemia.
Causes of low hemoglobin count
Normally low hemoglobin counts
A low hemoglobin count isn’t always a sign of illness — it may be normal for some people. Women who are pregnant commonly experience low hemoglobin counts.
Low hemoglobin counts associated with diseases and conditions
A low hemoglobin count can be associated with many diseases and conditions that cause your body to have too few red blood cells. This can occur if your body produces fewer red blood cells than usual, if your body destroys red blood cells faster than they can be produced, or if you experience blood loss.
Diseases and conditions that cause your body to produce fewer red blood cells than normal include:
- Aplastic anemia
- Certain medications, such as anti-retroviral drugs for HIV infection and chemotherapy drugs for cancer and other conditions
- Hodgkin’s lymphoma (Hodgkin’s disease)
- Hypothyroidism (a thyroid disorder)
- Iron deficiency anemia
- Kidney disease
- Lead poisoning
- Multiple myeloma
- Myelodysplastic syndromes
- Non-Hodgkin’s lymphoma
- Vitamin deficiency anemia
Diseases and conditions that cause your body to destroy red blood cells faster than they can be made:
- Enlarged spleen
- Sickle cell anemia
A low hemoglobin count can also be due to blood loss, which can occur because of:
- Bleeding from a wound
- Bleeding in your digestive or urinary tract
- Frequent blood donation
- Heavy menstrual periods
When to see a doctor
A low hemoglobin count is often discovered during a complete blood count test. If your test reveals you have a low hemoglobin count, ask your doctor what this means for you.
Make an appointment if you have signs and symptoms
If you experience signs and symptoms of a low hemoglobin count, make an appointment with your doctor. Signs and symptoms may include:
- Faster than normal heartbeat during exercise or activity
- Feeling short of breath
- Lack of energy during your usual activities
- Pale skin and gums
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.