Anemia

Anemia means the blood hemoglobin level is lower than normal for a person's age, sex and, in pregnancy, stage of pregnancy. Hemoglobin carries oxygen, so anemia can cause tiredness, weakness, breathlessness, pale skin, a fast heartbeat and dizziness. Mild anemia often causes no symptoms. Iron deficiency is the most common cause worldwide. Others include vitamin B12 or folate deficiency, long-term inflammation or kidney disease, blood loss, red cell breakdown (hemolysis), bone marrow problems, and inherited conditions such as thalassemia and sickle cell disease.

Lab tests linked to anemia:

• Hemoglobin: the test that defines anemia.
• Red blood cells (RBC): the red cell count, usually low in anemia.
• Transferrin: the protein that carries iron. It tends to rise in iron deficiency and fall with inflammation.
• Nucleated red blood cells (NRBC): immature red cells that are normally absent from adult blood. They can appear with severe anemia, marrow stress or bone marrow disease.
• White blood cells and absolute granulocyte count: checked to see whether other blood cell lines are also affected.
• Doctors also look at MCV, which sorts anemia by red cell size, and order ferritin, iron studies, a reticulocyte count, B12, folate, kidney function and a blood smear.

How results are read:

• Reference ranges for hemoglobin differ by age, sex, pregnancy and lab. Use the range on your report.
• Red cell size helps find the cause. Small cells point toward iron deficiency or thalassemia, large cells toward B12 or folate deficiency, alcohol or marrow problems, and normal-sized cells toward chronic disease, kidney disease or early blood loss.
• A low ferritin confirms iron deficiency. Ferritin can look falsely normal during inflammation.
• Abnormal white cell or platelet counts give extra clues. Some patterns call for investigation of a marrow disorder, while others occur with iron deficiency, infection or inflammation.

When to see a doctor:

• See a doctor to find the cause of any new anemia, especially unexplained iron deficiency in men or after menopause, which can be a sign of slow bleeding from the gut.
• Get emergency care for chest pain, severe breathlessness, fainting, vomiting blood, or black tarry stools.

Clinical takeaway: anemia is defined by a low hemoglobin, and red cell size, ferritin and reticulocytes help find the cause, which guides treatment.