About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- First decide whether the patient is unstable: chest pain, syncope, dyspnea at rest, hypotension, active bleeding, or heart failure changes the pathway.
- Classify by MCV and reticulocyte count: microcytic, normocytic, macrocytic, and marrow response.
- Iron deficiency in adult men and postmenopausal women is gastrointestinal blood loss until proven otherwise.
- Haemolysis pattern: high reticulocytes + high LDH/indirect bilirubin + low haptoglobin; add DAT if immune haemolysis suspected.
- Canadian patient blood management emphasizes treating the cause and using one-unit red cell transfusion with reassessment in stable, non-bleeding patients.
Approach to the Presentation
Anaemia (Approach to Low Hemoglobin) is approached as a clinical presentation rather than as a single diagnosis. Begin by assessing stability, bleeding or thrombosis risk, infection/sepsis features, medication exposures, pregnancy status where relevant, and systemic red flags. Then use the pattern of the abnormality — CBC lineage, smear morphology, coagulation pathway, node distribution, spleen size, or VTE pre-test probability — to select focused investigations. For MCCQE1, the safest answer is usually the one that identifies must-not-miss disease while avoiding reflex treatment of an isolated laboratory value.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Acute blood loss anaemia | must-not-miss | Hematemesis, melena, hematochezia, trauma, postpartum haemorrhage, heavy uterine bleeding, tachycardia or hypotension; early hemoglobin may be deceptively normal. | Serial CBC, type and screen/crossmatch, bleeding source assessment, response to resuscitation. |
| Occult gastrointestinal malignancy | must-not-miss | Iron deficiency in an adult man or postmenopausal woman, change in bowel habit, weight loss, abdominal mass, positive FIT, family history. | FIT plus colonoscopy and/or upper endoscopy according to local/provincial pathway. |
| Autoimmune haemolytic anaemia | must-not-miss | Fatigue, jaundice, dark urine, splenomegaly, recent infection, lymphoproliferative disease or drug exposure. | DAT positive, high reticulocytes, high LDH/indirect bilirubin, low haptoglobin, spherocytes. |
| Bone marrow failure or infiltration | must-not-miss | Anaemia with leukopenia and/or thrombocytopenia, infections, bruising, bone pain, B symptoms, abnormal smear. | CBC with differential and smear; urgent haematology referral for bone marrow aspirate/biopsy. |
| Iron deficiency anaemia | common | Microcytosis, high RDW, pica, restless legs, fatigue, koilonychia; menstrual loss, GI loss, pregnancy, low intake or malabsorption. | Low ferritin or low transferrin saturation; response to iron replacement. |
| Anaemia of inflammation / chronic disease | common | Normocytic or mildly microcytic anaemia with chronic infection, inflammatory disease, malignancy or CKD; ferritin normal/high. | Low serum iron and transferrin/TIBC with normal or high ferritin; assess underlying disease. |
| Vitamin B12 or folate deficiency | common | Macrocytosis, glossitis, neuropathy/posterior column signs for B12, vegan diet, metformin, PPI, pernicious anaemia. | B12 and folate levels; methylmalonic acid/homocysteine if equivocal; hypersegmented neutrophils. |
| Chronic kidney disease anaemia | common | Normocytic hypoproliferative anaemia with reduced eGFR, diabetes or hypertension history. | Creatinine/eGFR, urine ACR, low reticulocyte response; iron studies before ESA consideration. |
| Thalassaemia trait | less common | Marked microcytosis with relatively preserved hemoglobin and normal/high RBC count; family or ancestry risk. | Hemoglobin electrophoresis for beta-thalassaemia; alpha-thalassaemia may require genetic testing. |
| Myelodysplastic syndrome | less common | Older adult, macrocytosis, cytopenias, dysplastic neutrophils/platelets, infections or bruising. | Peripheral smear and bone marrow biopsy with cytogenetics. |
Red Flags & Key History
Symptoms
Chest pain, syncope, dyspnea at rest, confusion or heart failure symptoms — clinically significant tissue hypoxia
Melena, hematemesis, hematochezia, major trauma or postpartum bleeding — active blood loss
Weight loss, night sweats, anorexia, change in bowel habit or abdominal mass — possible malignancy
Jaundice, dark urine, back pain or recent new medication — consider haemolysis
Recurrent infections or mucosal bleeding alongside fatigue — marrow failure or pancytopenia
Pica, restless legs, heavy menstrual bleeding, pregnancy, low dietary intake — iron deficiency clues
Neuropathy, gait disturbance, cognitive change, vegan diet, metformin or PPI use — B12 clues
Signs
Hemodynamic instability, orthostatic hypotension, cool peripheries or altered mental status
Lymphadenopathy, hepatosplenomegaly, sternal tenderness, petechiae or purpura
Jaundice or scleral icterus suggesting haemolysis
Koilonychia, angular cheilitis or glossitis
Peripheral neuropathy or impaired vibration/proprioception
Approach to Investigation
First-line
CBC with differential and red cell indicesConfirm anaemia, classify by MCV, assess RDW, and identify other cytopenias or leukocytosis.
Reticulocyte countHigh reticulocytes suggest blood loss or haemolysis; low/inappropriately normal reticulocytes suggest underproduction.
Peripheral blood smearMicrocytosis, schistocytes, spherocytes, blasts, teardrops, hypersegmented neutrophils, rouleaux or dysplasia.
Ferritin, transferrin saturation, B12, folate, creatinine/eGFR, liver tests, TSHCore reversible-cause screen; interpret ferritin cautiously in inflammation.
Second-line
Haemolysis screenLDH, indirect bilirubin, haptoglobin, reticulocytes and DAT if immune haemolysis suspected.
Bleeding source evaluationFIT, urinalysis, pregnancy test where relevant, gynecologic assessment, and endoscopy/colonoscopy for appropriate risk groups.
Inflammation/systemic disease testsCRP/ESR, SPEP if rouleaux/back pain/renal dysfunction, celiac serology if malabsorption, HIV/hepatitis when indicated.
Specialist
Bone marrow aspirate and biopsyUnexplained cytopenias, blasts, dysplasia, pancytopenia, suspected MDS/aplastic anaemia/leukemia or marrow infiltration.
GI, gynecology, nephrology or haematology referralDriven by suspected source: GI cancer/bleeding, heavy uterine bleeding, CKD anaemia, haemolysis or marrow pathology.
Management Principles
Canadian Blood Services Clinical Guide to Transfusion + Choosing Wisely Canada transfusion recommendations1
Stabilize first
- ABCs, vitals, two large-bore IVs if bleeding, crystalloid judiciously, type and screen/crossmatch, and urgent source control.
- Transfuse based on symptoms, instability, active bleeding, cardiovascular disease and hemoglobin — not hemoglobin alone.
- In stable, non-bleeding patients use a restrictive strategy and transfuse one red cell unit at a time with reassessment.
2
Treat iron deficiency
- Oral iron if stable and absorption is likely; alternate-day dosing may improve tolerability.
- IV iron if oral iron is not tolerated, malabsorption is present, losses are substantial, late pregnancy requires rapid repletion, or response is inadequate.
- Find the cause: menstrual history in premenopausal patients; GI evaluation in adult men, postmenopausal women or alarm features.
3
Treat B12/folate deficiency
- Replace B12 before folate if both are possible to avoid worsening neurologic injury.
- Investigate pernicious anaemia, malabsorption, diet, alcohol and medication causes.
4
Treat haemolysis or marrow disease
- Warm immune haemolysis usually needs urgent haematology input and corticosteroids after appropriate testing.
- Schistocytes with thrombocytopenia/AKI/neuro features: treat as TTP until proven otherwise.
- Suspected leukemia, aplastic anaemia or MDS: urgent haematology referral.
Complications & Pitfalls
- Do not transfuse iron deficiency by default: stable patients usually need iron and investigation of the cause.
- Do not miss colon cancer: iron deficiency in an adult man or postmenopausal woman is occult GI blood loss until proven otherwise.
- MCV can mislead: mixed iron and B12 deficiency may produce a normal MCV.
- Schistocytes are an emergency: microangiopathic haemolysis with thrombocytopenia requires urgent escalation.
- Check prior CBCs: chronic mild anaemia and acute severe anaemia carry different risk.
MCCQE1 Exam Tips
- 1Start with MCV + reticulocytes + smear: that is the MCC pattern-recognition core.
- 2Microcytic anaemia with low ferritin in an adult man or postmenopausal woman requires GI evaluation.
- 3High reticulocytes means blood loss or haemolysis; low reticulocytes means marrow under-response.
- 4Neurologic findings plus macrocytosis = B12 deficiency until proven otherwise.
- 5Schistocytes + thrombocytopenia + renal or neurologic findings = TTP/HUS/DIC pattern.
- 6Stable non-bleeding patient: one unit then reassess, or no transfusion if iron therapy is appropriate.
- 7CanMEDS communicator angle: explain that iron deficiency is a sign, not a final diagnosis.
practicetest your knowledge on anaemia (approach to low hemoglobin)Apply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — haematologic & oncologic and beyond.
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