Anemia Detected
Hgb <13 g/dL (men) or <12 g/dL (women)
All Pathways
Internal MedicineDiagnostic
Anemia Diagnostic Workup
Anemia Diagnostic Workup: Anemia Detected → Initial Labs → MCV Classification → Microcytic Anemia (MCV <80) → Iron Studies Pattern.
Pathway Overview
18 steps
Algorithm Steps
18 total
01Start 02Action Initial Labs
Complete evaluation
- CBC with indices (MCV, MCH, MCHC, RDW)
- Reticulocyte count
- Peripheral smear
- Basic metabolic panel (renal function)
03Decision MCV Classification
Key to differential diagnosis
- Microcytic: MCV <80 fL
- Normocytic: MCV 80-100 fL
- Macrocytic: MCV >100 fL
04Action Microcytic Anemia (MCV <80)
Check iron studies first
- Iron, ferritin, TIBC, transferrin saturation
- Think: TICS - Thalassemia, Iron deficiency, Chronic disease, Sideroblastic
05Decision Iron Studies Pattern
Ferritin and TIBC interpretation
- Low ferritin = iron deficiency
- High ferritin, low iron = chronic disease
- Normal iron studies = thalassemia screen
06Action Iron Deficiency Anemia
Low ferritin (<30), high TIBC
- Find source of blood loss
- GI workup if no obvious source (EGD/colonoscopy)
- GYN evaluation if menorrhagia
- Treat: oral iron (ferrous sulfate 325mg TID)
- Recheck Hgb in 4-8 weeks
07Action Anemia of Chronic Disease
High ferritin, low iron/TIBC
- Inflammatory block of iron utilization
- Treat underlying condition
- ESA if renal disease (EPO low)
- IV iron may help if functional iron deficiency
08Action Consider Thalassemia
Normal iron, microcytic, target cells
- Hgb electrophoresis
- Beta-thal trait: elevated HbA2
- Alpha-thal: genetic testing
- Usually no treatment needed for trait
09Action Normocytic Anemia (MCV 80-100)
Most common; broad differential
- Check reticulocyte count first
- Renal function (EPO-related)
- Consider: anemia of chronic disease, early iron deficiency, hemolysis, bone marrow
10Decision Reticulocyte Count
Bone marrow response
- Low/normal retic: underproduction
- High retic (>2%): hemolysis or blood loss
11Action Underproduction (Low Retic)
Bone marrow not responding
- Check EPO level
- Renal disease (low EPO)
- Chronic disease (inflammation)
- Consider bone marrow if unexplained
12Warning Hematology Referral
When to refer
- Unexplained cytopenias
- Suspected bone marrow disorder
- Hemolysis workup
- Transfusion-dependent anemia
- Suspected MDS, aplastic anemia
13Action Hemolysis (High Retic)
Destruction of RBCs
- LDH elevated, haptoglobin low
- Indirect bilirubin elevated
- DAT (Coombs) for immune hemolysis
- Smear: spherocytes, schistocytes
- Path rejoins step 12Shared downstream outcome
14Action Macrocytic Anemia (MCV >100)
B12/folate vs non-megaloblastic
- Check B12, folate, TSH, LFTs
- Reticulocyte count
- Consider: alcohol, hypothyroidism, MDS, liver disease
15Decision B12/Folate Levels
Megaloblastic vs non-megaloblastic
16Action B12 Deficiency
B12 <200 pg/mL
- Check methylmalonic acid if borderline
- Causes: pernicious anemia, malabsorption, vegan diet
- Treat: B12 1000mcg IM daily x7d, then weekly x4, then monthly
- Or high-dose oral (1000-2000mcg daily)
17Action Folate Deficiency
Folate <3 ng/mL, normal B12
- Causes: poor intake, alcohol, malabsorption
- Treat: folic acid 1mg daily
- Rule out B12 deficiency first (can mask)
18Action Non-Megaloblastic Macrocytic
Normal B12/folate
- Alcohol (most common)
- Hypothyroidism
- Liver disease
- Reticulocytosis
- MDS, aplastic anemia (need BMBx)
Guideline Source
Systematic Approach to Anemia Based on MCV
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- Does not cover rare causes of anemia
- Bone marrow biopsy indications simplified
- Hemolytic workup may need hematology
- Pediatric values differ
- Does not address transfusion thresholds
Applicable Regions
USEUGlobal
Global: MCV classification universally applicable
Version 1Next review: 2027-01-11
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Related Resources
Frequently Asked Questions
What is the Anemia Diagnostic Workup?
The Anemia Diagnostic Workup is a diagnostic clinical algorithm for Internal Medicine. It provides a structured decision tree to guide clinical decision-making, based on Systematic Approach to Anemia Based on MCV.
What guideline is the Anemia Diagnostic Workup based on?
This algorithm is based on Systematic Approach to Anemia Based on MCV.
What are the limitations of the Anemia Diagnostic Workup?
Known limitations include: Does not cover rare causes of anemia; Bone marrow biopsy indications simplified; Hemolytic workup may need hematology; Pediatric values differ; Does not address transfusion thresholds. Individual patient factors may require deviation from these recommendations.
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