Anemia details
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Anemia means a reduced oxygen-carrying capacity of blood, usually because hemoglobin or red blood cell mass is low. It is a finding, not a single disease, so the cause needs to be identified.
- Classification - microcytic, normocytic, and macrocytic anemia based on MCV
- Causes - iron deficiency, blood loss, vitamin B12/folate deficiency, chronic disease/inflammation, kidney disease, hemolysis, marrow disorders, inherited conditions
- Symptoms and signs - fatigue, pallor, shortness of breath, palpitations, dizziness; severe anemia can cause chest pain or fainting
- Diagnosis - CBC with indices, reticulocyte count, peripheral smear, iron studies, B12/folate, kidney tests, and tests for bleeding or hemolysis as indicated
- Treatment - treats the underlying cause; iron, B12 or folate replacement are appropriate only when deficiency is confirmed; transfusion is reserved for selected urgent/severe situations
- Red flags - black or bloody stool, heavy ongoing bleeding, fainting, chest pain, breathing difficulty, or rapidly worsening weakness need urgent assessment
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- Types and causes
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- Iron-deficiency anemia
- Treatment and diet
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Please tell me which anemia topic you want:
- Types and causes
- Symptoms and diagnosis
- Iron-deficiency anemia
- Treatment and diet
- Short exam notes
Normal values and etiology
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WHO haemoglobin concentrations diagnosis anaemia 2024 guideline thresholds adults children pregnancy
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Normal hemoglobin values and anemia cutoffs
Hemoglobin values vary by age, sex, pregnancy, altitude, smoking, and laboratory method. The following are WHO 2024 sea-level cutoffs:
| Group | Normal hemoglobin | Anemia if Hb is below |
|---|---|---|
| Adult men, 15-65 years | ≥13.0 g/dL | 13.0 g/dL |
| Non-pregnant adult women, 15-65 years | ≥12.0 g/dL | 12.0 g/dL |
| Pregnancy, 1st trimester | ≥11.0 g/dL | 11.0 g/dL |
| Pregnancy, 2nd trimester | ≥10.5 g/dL | 10.5 g/dL |
| Pregnancy, 3rd trimester | ≥11.0 g/dL | 11.0 g/dL |
| Children 6-23 months | ≥10.5 g/dL | 10.5 g/dL |
| Children 24-59 months | ≥11.0 g/dL | 11.0 g/dL |
| Children 5-11 years | ≥11.5 g/dL | 11.5 g/dL |
| Children 12-14 years | ≥12.0 g/dL | 12.0 g/dL |
These are diagnostic thresholds, rather than a complete laboratory reference range. Results should be adjusted/interpreted for altitude and smoking. The WHO hemoglobin guideline gives the current cutoffs.
Common adult red-cell reference values
These vary slightly among laboratories.
| Test | Typical adult reference range |
|---|---|
| Hemoglobin, male | 13.5-17.5 g/dL |
| Hemoglobin, female | 12.0-15.5 g/dL |
| Hematocrit, male | 41%-53% |
| Hematocrit, female | 36%-46% |
| RBC count, male | 4.5-5.9 million/µL |
| RBC count, female | 4.1-5.1 million/µL |
| MCV | 80-100 fL |
| MCH | 27-33 pg |
| MCHC | 32-36 g/dL |
| Reticulocyte count | about 0.5%-2.5% of RBCs |
Etiology of anemia
Anemia results from one or more of three mechanisms:
1. Blood loss
- Acute: trauma, surgery, ruptured ectopic pregnancy, gastrointestinal bleeding
- Chronic: heavy menstrual bleeding, peptic ulcer, hemorrhoids, colon cancer/polyps, hookworm infestation, repeated blood donation
Chronic blood loss commonly produces iron-deficiency, microcytic anemia.
2. Reduced red-cell production
Nutritional deficiencies
- Iron deficiency: poor intake, malabsorption, increased need in pregnancy/growth, chronic blood loss
- Vitamin B12 deficiency: pernicious anemia, vegan diet without supplementation, gastric/ileal disease or surgery
- Folate deficiency: poor diet, alcohol use, malabsorption, increased demand, certain medicines
Chronic disease
- Anemia of inflammation/chronic disease: chronic infections, autoimmune disease, cancer
- Chronic kidney disease: reduced erythropoietin production, iron restriction from inflammation, and reduced RBC survival. Tietz Textbook of Laboratory Medicine, p. 1872
- Liver disease, hypothyroidism
Bone-marrow disorders
- Aplastic anemia
- Myelodysplastic syndrome
- Leukemia, lymphoma, myeloma, marrow infiltration
- Drugs, chemotherapy, radiation, toxins
3. Increased red-cell destruction: hemolytic anemia
- Inherited: sickle cell disease, thalassemia, G6PD deficiency, hereditary spherocytosis
- Acquired: autoimmune hemolytic anemia, malaria, mechanical heart valves, severe burns, microangiopathic disorders such as TTP/HUS
Etiology by MCV
| Type | MCV | Important causes |
|---|---|---|
| Microcytic | <80 fL | Iron deficiency, thalassemia, anemia of inflammation, sideroblastic anemia, lead toxicity |
| Normocytic | 80-100 fL | Acute blood loss, hemolysis, chronic kidney disease, inflammation, endocrine disease, marrow failure |
| Macrocytic | >100 fL | Vitamin B12/folate deficiency, alcohol use, liver disease, hypothyroidism, drugs, myelodysplasia |
A raised reticulocyte count suggests appropriate marrow response, usually from blood loss or hemolysis. A low or inappropriately normal reticulocyte count suggests impaired red-cell production.
Symptom in child and normal Early late
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Anemia in children: early and late symptoms
Many children with mild or slowly developing anemia have no obvious symptoms. Symptoms depend on how low the hemoglobin is and how quickly it falls.
Early or mild symptoms
- Tiredness, less active play
- Weakness or easy fatigue
- Irritability, poor attention, poor school performance
- Reduced appetite or poor feeding in infants
- Mild pallor: pale palms, nail beds, lips, tongue, or inner eyelids
- Poor weight gain or slow growth if anemia is long-standing
- Pica: eating non-food items such as soil, clay, paper, or ice, especially in iron deficiency
Late or severe symptoms
- Marked pallor, lethargy, excessive sleepiness
- Fast heartbeat or palpitations
- Rapid breathing, shortness of breath, exercise intolerance
- Dizziness, headache, fainting
- Cold hands and feet, delayed capillary refill
- Swelling of feet or face
- Heart failure in severe anemia: breathing difficulty at rest, enlarged liver, poor feeding/sweating in infants
Symptoms pointing to a particular cause
- Jaundice, dark urine, enlarged spleen: possible hemolysis
- Bone pain, fever, repeated infections, bruising/bleeding: may suggest marrow disease and needs prompt evaluation
- Heavy worms, blood in stool, or heavy menstrual bleeding in adolescents: possible chronic blood loss
Normal hemoglobin in children
WHO 2024 sea-level thresholds:
| Age | Normal Hb | Anemia if Hb is below |
|---|---|---|
| 6-23 months | ≥10.5 g/dL | <10.5 g/dL |
| 24-59 months | ≥11.0 g/dL | <11.0 g/dL |
| 5-11 years | ≥11.5 g/dL | <11.5 g/dL |
| 12-14 years | ≥12.0 g/dL | <12.0 g/dL |
The WHO thresholds vary with altitude, smoking exposure, age, and physiological circumstances. See the WHO hemoglobin cutoffs.
When urgent medical care is needed
Seek urgent care if a child has:
- Difficulty breathing, rapid breathing at rest, or chest discomfort
- Fainting, extreme drowsiness, confusion, or seizures
- Severe weakness or inability to feed/drink
- Fast heartbeat with cold extremities
- Pallor with jaundice or dark urine
- Active bleeding, black stool, or bloody stool
A CBC with hemoglobin, MCV, peripheral smear, reticulocyte count, and iron studies is usually used to confirm anemia and identify its cause.
Diagnosis
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pediatric anemia diagnostic evaluation CBC reticulocyte ferritin official guideline
Diagnosis of anemia in a child
1. Confirm anemia
Start with a complete blood count (CBC):
- Hemoglobin (Hb) and hematocrit (Hct)
- RBC count
- MCV: classifies anemia as microcytic, normocytic, or macrocytic
- MCH/MCHC and RDW
- White blood cell and platelet counts
Use hemoglobin values appropriate to the child’s age. For example, anemia is Hb <10.5 g/dL at 6-23 months, <11 g/dL at 24-59 months, <11.5 g/dL at 5-11 years, and <12 g/dL at 12-14 years.
2. Clinical history and examination
Ask about:
- Diet: excess cow’s milk, inadequate iron-containing food, pica
- Prematurity, low birth weight
- Fever, chronic illness, kidney disease, malabsorption
- Bleeding: nose bleed, black/bloody stools, worms, heavy menstrual periods in adolescents
- Jaundice or dark urine
- Medicine, toxin, or lead exposure
- Family history of thalassemia, sickle cell disease, or hemolytic anemia
Examine for pallor, jaundice, bruising/petechiae, lymph nodes, liver or spleen enlargement, growth failure, heart rate, respiratory distress, and signs of infection.
3. Core tests to identify the cause
- Peripheral blood smear: cell size, shape, hypochromia, target cells, fragments, blasts
- Reticulocyte count: assesses marrow response
- Iron studies: ferritin, serum iron, TIBC/transferrin, transferrin saturation
- Stool examination: occult blood or parasites if indicated
- Hemoglobin electrophoresis/HPLC: thalassemia or sickle-cell disease
- Vitamin B12 and folate: when macrocytosis or dietary risk exists
- Renal function, liver function, thyroid tests, CRP/ESR: as clinically indicated
- Lead level: if environmental exposure or unexplained microcytosis
- Direct antiglobulin test (DAT/Coombs), bilirubin, LDH, haptoglobin: if hemolysis is suspected
Initial evaluation generally includes CBC with indices, peripheral smear, and reticulocyte count. A high reticulocyte count suggests blood loss or hemolysis; a low/inappropriately normal count suggests inadequate RBC production. This approach is described in a pediatric anemia review.
Diagnostic approach by MCV
| Type | MCV | Common causes | Helpful next tests |
|---|---|---|---|
| Microcytic | <80 fL | Iron deficiency, thalassemia, inflammation, lead toxicity | Ferritin and iron profile; Hb electrophoresis; lead level if risk |
| Normocytic | 80-100 fL | Acute bleeding, hemolysis, chronic disease, kidney disease, marrow suppression | Reticulocyte count, smear, bilirubin/LDH/DAT, renal function |
| Macrocytic | >100 fL | B12/folate deficiency, liver disease, hypothyroidism, marrow disorders, drugs | B12, folate, thyroid/liver tests, smear; consider marrow evaluation if unexplained |
Typical diagnostic patterns
| Condition | CBC / smear pattern | Confirmatory clues |
|---|---|---|
| Iron-deficiency anemia | Low Hb, low MCV/MCH, high RDW, microcytic hypochromic cells | Low ferritin, low serum iron and transferrin saturation, raised TIBC |
| Thalassemia trait | Marked microcytosis with relatively preserved/high RBC count | Hb electrophoresis or genetic testing; ferritin may be normal |
| Anemia of inflammation | Usually normocytic, sometimes mildly microcytic | Low iron, low/normal TIBC, normal/high ferritin, raised inflammatory markers |
| Hemolytic anemia | Often normocytic with high reticulocytes | Jaundice, high indirect bilirubin/LDH, low haptoglobin; DAT may be positive |
| Marrow failure/leukemia | Low reticulocyte count, possibly low WBCs and platelets | Blasts/abnormal cells on smear, marrow examination if needed |
| B12/folate deficiency | Macrocytosis, hypersegmented neutrophils | Low B12 or folate level |
Important warning signs
Urgent pediatric assessment is needed for severe pallor with breathing difficulty, fainting, lethargy, rapid heartbeat, poor feeding, jaundice/dark urine, active bleeding, fever with bruising, enlarged liver/spleen, lymph nodes, or low WBCs/platelets along with anemia.
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