Anemia

Causes

• Blood loss:
  • Acute blood loss: This can occur due to sudden events such as surgery, injury, or gastrointestinal bleeding (e.g., from ulcers or colon cancer).
  • Chronic blood loss: This can result from long-term conditions such as heavy menstrual periods, slow gastrointestinal bleeding, or frequent blood donation.
• Decreased red blood cell production:
  • Iron deficiency anemia: This is the most common type of anemia and occurs when the body doesn't have enough iron to produce hemoglobin, the protein in red blood cells that carries oxygen. Causes include inadequate dietary iron, poor iron absorption, and chronic blood loss.
  • Vitamin deficiency anemia: Deficiencies in vitamin B12 or folate can impair red blood cell production. Causes include inadequate dietary intake, poor absorption (e.g., pernicious anemia), or increased need (e.g., during pregnancy).
  • Anemia of chronic disease: Chronic inflammatory conditions such as rheumatoid arthritis, kidney disease, and cancer can interfere with red blood cell production.
  • Aplastic anemia: This rare condition occurs when the bone marrow fails to produce enough red blood cells, white blood cells, and platelets. It can be caused by autoimmune disorders, infections, exposure to toxins, or certain medications.
  • Myelodysplastic syndromes: These are a group of disorders in which the bone marrow produces abnormal blood cells.
• Increased red blood cell destruction (hemolysis):
  • Hereditary hemolytic anemias: These are inherited conditions in which red blood cells are fragile and easily destroyed. Examples include sickle cell anemia, thalassemia, and hereditary spherocytosis.
  • Acquired hemolytic anemias: These conditions occur when the body's immune system mistakenly attacks and destroys red blood cells. They can be caused by autoimmune diseases, infections, medications, or blood transfusions.

Symptoms

• Fatigue
• Weakness
• Pale or yellowish skin
• Shortness of breath
• Dizziness or lightheadedness
• Headaches
• Cold hands and feet
• Brittle nails
• Rapid or irregular heartbeat
• Chest pain

Diagnosis

• Complete blood count (CBC): This is the most common test used to diagnose anemia. It measures several components of the blood, including:
  • Hemoglobin level: The amount of oxygen-carrying protein in red blood cells.
  • Hematocrit: The percentage of blood volume made up of red blood cells.
  • Red blood cell count: The number of red blood cells.
  • Red blood cell indices: These measurements provide information about the size and shape of red blood cells, which can help determine the cause of anemia.
  • Peripheral blood smear: This test involves examining a sample of blood under a microscope to look at the size, shape, and maturity of red blood cells.
  • Reticulocyte count: This test measures the number of young red blood cells, which can help determine if the bone marrow is producing enough red blood cells.
  • Iron studies: These tests measure the levels of iron, ferritin (stored iron), and transferrin (a protein that carries iron) in the blood. They are used to diagnose iron deficiency anemia.
  • Vitamin B12 and folate levels: These tests measure the levels of these vitamins in the blood and are used to diagnose vitamin deficiency anemia.
  • Bone marrow biopsy: This test is sometimes necessary to diagnose certain types of anemia, such as aplastic anemia or myelodysplastic syndromes.

Treatment

• Iron deficiency anemia:
  • Iron supplements: Oral iron supplements are the most common treatment.
  • Dietary changes: Eating iron-rich foods such as red meat, beans, and leafy green vegetables can help.
  • Treatment of underlying cause: If the anemia is caused by blood loss, the source of the bleeding needs to be identified and treated.
• Vitamin deficiency anemia:
  • Vitamin B12 injections or supplements: Pernicious anemia, caused by poor vitamin B12 absorption, is usually treated with B12 injections.
  • Folate supplements: Folic acid supplements can treat folate deficiency anemia.
  • Dietary changes: Eating foods rich in vitamin B12 (meat, dairy) and folate (leafy greens, beans) is important.
• Anemia of chronic disease:
  • Treatment of the underlying disease: Managing the chronic condition is the primary goal.
  • Erythropoiesis-stimulating agents (ESAs): Medications like erythropoietin can stimulate red blood cell production in some cases, but they carry risks.
  • Blood transfusions: May be necessary in severe cases.
• Aplastic anemia:
  • Blood transfusions: To manage low red blood cell counts.
  • Bone marrow transplantation: This can be a curative treatment in some cases.
  • Immunosuppressive therapy: Medications to suppress the immune system may be used.
• Hereditary hemolytic anemias:
  • Treatment varies depending on the specific condition and may include:
    • Blood transfusions
    • Medications
    • Surgery (e.g., splenectomy in some cases of hereditary spherocytosis)
• Acquired hemolytic anemias:
  • Treatment of the underlying cause: Addressing the autoimmune disease, infection, or medication causing the hemolysis.
  • Corticosteroids or other immunosuppressive drugs: To suppress the immune system.
  • Blood transfusions: In severe cases.

Finding the Cause Is the Treatment

Anemia is a laboratory finding, not a diagnosis, and treating the number without finding the reason is how serious causes get missed. The workup is usually short, and it determines everything that follows.

Iron deficiency in an adult needs an explanation

In men and in women past menopause, iron deficiency means blood loss from the gut until proven otherwise, and a colonoscopy and upper endoscopy are the standard response even when there are no digestive symptoms. In menstruating women, heavy periods are the most common cause but not the only one, and our iron deficiency in women guide covers when to look further. Celiac disease is tested for in anyone whose iron deficiency has no obvious source, because it blocks absorption silently.

Ferritin is the number to ask about

Hemoglobin falls late. Ferritin, which measures stored iron, drops first, and a value below about 30 ng/mL means iron deficiency even when hemoglobin is still normal. Ferritin also rises with inflammation, so a normal value in someone with arthritis, infection, or kidney disease can hide a real deficiency, and other iron studies are used to sort that out. Our guide to blood work explains the rest of the panel.

Taking iron so it works

Oral iron is absorbed better and tolerated better taken every other day than daily, and taken away from calcium, coffee, tea, and acid-suppressing medication. Repleting stores takes three to six months, not the two weeks it takes to feel better, and stopping early is the usual reason deficiency returns. Intravenous iron is used when tablets fail or are not tolerated, and routinely in chronic kidney disease and inflammatory bowel disease.

B12 deficiency hides behind common medications

Metformin and long-term acid suppression both lower B12 absorption, and older adults absorb it poorly regardless. Nerve symptoms such as numbness, balance problems, and memory change can appear before the blood count moves, and they may not fully reverse if treatment is delayed; the vitamin B12 deficiency page covers testing and replacement.

When anemia needs a hematologist, and when it needs the emergency room

Anemia with no cause found, abnormal white cells or platelets alongside it, or a poor response to replacement warrants referral to our hematology team, since bone marrow disorders become more common with age. Chest pain, breathlessness at rest, fainting, or black or bloody stools mean urgent evaluation the same day. The NHLBI and the American Society of Hematology publish patient guidance on types and treatment.

If you have been told you are anemic and were given iron without anyone asking why, schedule a visit; the reason matters more than the pill.