Haemoglobin (Hb) is oxygen carrying protein in your blood cells.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.

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. 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
  • Cancer
  • Certain medications, such as anti-retroviral drugs for HIV infection and chemotherapy drugs for cancer and other conditions
  • Cirrhosis
  • Hodgkin’s lymphoma (Hodgkin’s disease)
  • Hypothyroidism (a thyroid disorder)
  • Iron deficiency anemia
  • Kidney disease
  • Leukemia
  • 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
  • Porphyria
  • Sickle cell anemia
  • Thalassemia
  • Vasculitis
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
  • Nosebleeds