Anemia is a reduction in hemoglobin (Hb) or red blood cell (RBC) mass that lowers the blood's oxygen-carrying capacity. Common thresholds (WHO) are Hb below 13 g/dL (130 g/L) in men and below 12 g/dL (120 g/L) in nonpregnant women (about 11 g/dL in pregnancy, with a slightly lower cutoff in the second trimester). Anemia is a sign, not a diagnosis — the cause must be found.

Three mechanisms

1. Blood loss — acute (trauma, GI bleeding) or chronic (menstruation, occult GI bleeding)
2. Decreased RBC production — iron, vitamin B12, or folate deficiency; bone marrow failure (aplastic anemia); chronic kidney disease (too little erythropoietin); chronic inflammation
3. Increased RBC destruction (hemolysis) — sickle cell disease, thalassemia, G6PD deficiency, autoimmune hemolytic anemia, mechanical valves, transfusion reactions

Classification by red cell size (MCV)

Key types

• Iron deficiency anemia — the most common anemia worldwide. In women of reproductive age, heavy menstrual bleeding is the most common cause; in men and postmenopausal women, suspect gastrointestinal blood loss (including cancer). Also pregnancy, poor intake, malabsorption (celiac disease, bariatric surgery)
• Anemia of inflammation (chronic disease) — inflammatory cytokines raise hepcidin, which traps iron in storage so it cannot be used for RBC production; RBC survival is also shortened
• Anemia of chronic kidney disease — mainly erythropoietin deficiency
• Vitamin B12 deficiency — pernicious anemia (autoimmune loss of intrinsic factor), gastrectomy or bariatric surgery, ileal disease, strict vegan diet, long-term metformin or acid suppression. Causes megaloblastic anemia and nerve damage
• Folate deficiency — poor diet, alcohol use, pregnancy, methotrexate, phenytoin. Megaloblastic anemia without neurologic damage
• Aplastic anemia — bone marrow failure → pancytopenia (low RBCs, WBCs, platelets). Usually autoimmune; also drugs, radiation, benzene, viral hepatitis
• Hemolytic anemias — sickle cell disease (HbS polymerizes when deoxygenated, cells sickle and block small vessels), thalassemia (reduced globin chain production), G6PD deficiency (oxidant stress triggers hemolysis), autoimmune hemolytic anemia (antibodies coat RBCs)

General (any anemia): fatigue and weakness, pallor (conjunctiva, palms, nail beds), dyspnea on exertion, tachycardia, palpitations, headache, dizziness, orthostatic hypotension, cold intolerance. Severe anemia can cause angina or high-output heart failure. The priority nursing problem is usually fatigue/activity intolerance related to decreased oxygen-carrying capacity.

Iron deficiency

• Find and treat the cause (menstrual disorder, GI lesion)
• Oral iron (e.g., ferrous sulfate) once daily or every other day — alternate-day dosing may improve absorption and tolerance. Continue about 3 months after Hb normalizes to refill stores. Reticulocytes rise within about 7–10 days; Hb rises over several weeks
• IV iron (iron sucrose, ferric carboxymaltose, ferric derisomaltose) for intolerance, malabsorption, ongoing losses, CKD, or pregnancy with severe deficiency. Monitor for hypersensitivity reactions and hypotension and observe for at least 30 minutes after the infusion; extravasation causes permanent brown skin staining; ferric carboxymaltose can cause low phosphate
• Oral iron adverse effects: nausea, constipation, dark or black stools (expected). Accidental overdose is dangerous in children

Anemia of CKD

• Erythropoiesis-stimulating agents (ESAs) — epoetin alfa, darbepoetin alfa — plus iron as needed. Adverse effects: hypertension, thrombosis, stroke, seizures; higher Hb targets increase cardiovascular events, so doses are reduced when Hb approaches about 11 g/dL (110 g/L). Monitor BP and Hb regularly

Vitamin B12 deficiency

• Cyanocobalamin or hydroxocobalamin IM (frequent doses initially, then monthly); lifelong for pernicious anemia. High-dose oral B12 is an effective alternative for many clients, including some with pernicious anemia, if adherence and follow-up are reliable
• Check potassium early in treatment of severe megaloblastic anemia (rapid cell production can cause hypokalemia)

Folate deficiency: oral folic acid. Always rule out B12 deficiency first — folic acid corrects the anemia but lets B12 nerve damage progress.

Aplastic anemia: hematopoietic stem cell transplant (younger clients with a matched donor) or immunosuppressive therapy (antithymocyte globulin + cyclosporine, often with eltrombopag); transfusion support; prompt treatment of infection.

Autoimmune hemolytic anemia (warm type): corticosteroids (prednisone) first-line; rituximab or splenectomy for relapse. Steroid adverse effects: hyperglycemia, hypertension, fluid retention, hypokalemia, infection, GI bleeding, mood changes, osteoporosis; taper, do not stop abruptly.

Sickle cell disease

• Vaso-occlusive crisis: rapid, effective analgesia — current guidance aims for the first dose within about 60 minutes of arrival, usually IV opioids, reassessed every 30–60 minutes — plus hydration (IV or oral) to reduce sickling, while avoiding fluid overload. Oxygen only if hypoxemic. Avoid meperidine
• Hydroxyurea — raises fetal hemoglobin and reduces crises; myelosuppression (monitor CBC), teratogenic (contraception required). Other options: L-glutamine, crizanlizumab (availability varies by country), chronic transfusion, stem cell transplant, gene therapy. Voxelotor was withdrawn worldwide in 2024 for safety reasons and should not be used
• Acute chest syndrome: new lung infiltrate with fever, chest pain, or hypoxemia — antibiotics, oxygen, transfusion; incentive spirometry helps prevent it

Thalassemia major: regular transfusions with iron chelation (deferasirox — kidney/liver toxicity; deferoxamine — hearing and vision changes; deferiprone — agranulocytosis, weekly neutrophil counts). Do not give iron to clients with thalassemia unless iron deficiency is proven.

Transfusion: for most stable hospitalized adults, a restrictive threshold of Hb 7 g/dL (70 g/L) is used; 7.5 g/dL for cardiac surgery; 8 g/dL for orthopedic surgery or preexisting cardiovascular disease; a higher threshold may be used in acute MI per cardiology. Symptoms also guide the decision.

Transfusion reactions to recognize: acute hemolytic (fever, flank or back pain, hypotension, dark urine); febrile nonhemolytic; allergic or anaphylactic; TACO — circulatory overload (hypertension, crackles, raised BNP — slow the rate, diuretic as ordered); TRALI — hypoxemia and noncardiogenic pulmonary edema within 6 hours. Use only 0.9% saline with blood and complete each unit within 4 hours.

Listed in priority order.

1. Oxygenation and perfusion — assess SpO₂, heart rate, BP, chest pain, dyspnea; give oxygen if hypoxemic; for acute blood loss, IV access and prepare for transfusion
2. Aplastic anemia and neutropenia — infection prevention is the top priority: strict hand hygiene and aseptic technique, avoid ill visitors, monitor temperature, report fever immediately
3. Bleeding precautions when platelets are low — soft toothbrush, electric razor, no IM injections if avoidable, fall prevention
4. Sickle cell crisis — do not delay pain relief; start hydration; keep warm (no cold packs); incentive spirometry; monitor for acute chest syndrome, stroke signs, splenic sequestration
5. Transfusion safety — two-person identification; stay with the client for the first 15 minutes; stop the transfusion and keep the IV open with normal saline via new tubing for any reaction
6. Fatigue — cluster care, rest periods, gradual activity progression; rise slowly (orthostatic dizziness)
7. Nutrition — iron-, folate-, and B12-rich foods as appropriate; mouth care for glossitis

• Oral iron: best absorbed on an empty stomach (about 1 hour before meals) with vitamin C (orange juice). If stomach upset occurs, take it with or right after food — absorption is lower but adherence is better
• Separate iron by 2 hours from milk, calcium, antacids, tea, and coffee, and from levothyroxine, tetracyclines, and fluoroquinolones
• Expect dark or black stools; report tarry stools with abdominal pain or dizziness. Increase fluids and fiber for constipation. Take liquid iron through a straw to avoid staining teeth. Store out of children's reach
• Iron-rich foods: red meat, liver, poultry, fish, legumes, dark green vegetables, fortified cereals
• Women: report heavy or prolonged menstrual bleeding — menstrual history is essential in iron deficiency
• B12 deficiency: injections or pills are often lifelong for pernicious anemia; strict vegans need a B12 supplement
• Sickle cell disease: drink plenty of fluids, avoid cold, high altitude, and overexertion; stay current on vaccines (pneumococcal, meningococcal, influenza); seek care for fever of 38.5 °C (101.3 °F) or higher (or the lower threshold in your care plan), chest pain, breathing difficulty, or neurologic changes
• G6PD deficiency: avoid fava beans, naphthalene mothballs, and trigger drugs (e.g., primaquine, dapsone, sulfonamides, rasburicase) — tell every prescriber
• ESA therapy: keep BP checks and blood tests; report headache, chest pain, leg swelling, or neurologic symptoms

• Iron deficiency: microcytic, low ferritin, high TIBC; women → ask about menstrual bleeding; men and older adults → look for GI blood loss
• Oral iron: empty stomach with vitamin C is ideal; take with food if GI upset; avoid milk, antacids, tea, and coffee; black stools expected
• B12 deficiency: macrocytic, beefy-red tongue, paresthesias, loss of position sense, dementia-like changes; pernicious anemia needs lifelong B12
• Rule out B12 deficiency before treating with folic acid alone
• Anemia of CKD = erythropoietin deficiency → ESA; watch hypertension and thrombosis
• Anemia of inflammation = iron trapped by hepcidin; ferritin normal/high
• Aplastic anemia = pancytopenia; infection prevention is the top priority
• Hemolysis = jaundice, splenomegaly, high LDH and indirect bilirubin, low haptoglobin
• Corticosteroids → hyperglycemia and hypertension
• Sickle cell crisis: rapid analgesia plus hydration; oxygen only if hypoxemic; voxelotor withdrawn
• Most stable adults: transfuse at Hb below 7 g/dL (70 g/L)