What is the appropriate management for a patient with low hemoglobin (Hb) and hematocrit (Hct) levels?

Management of Low Hemoglobin and Hematocrit

For patients with low hemoglobin and hematocrit, immediately evaluate for iron deficiency and other correctable causes before considering erythropoiesis-stimulating agents (ESAs), with iron supplementation as first-line therapy for iron deficiency anemia. 1, 2

Initial Diagnostic Workup

When hemoglobin or hematocrit falls below normal ranges, perform the following tests:

• Complete blood count (CBC) with red blood cell indices (MCV, MCH, MCHC) 1, 2
• Iron studies: serum iron, total iron-binding capacity (TIBC), transferrin saturation (TSAT), and serum ferritin 1
• Reticulocyte count to assess bone marrow response 1
• White blood cell and platelet counts to exclude broader bone marrow dysfunction 1

Critical caveat: Hemoglobin and hematocrit alone are insufficient for diagnosis—they only decrease with severe iron depletion and can miss early iron deficiency. 3 Normal CBC values do not exclude iron deficiency if ferritin and serum iron are low. 3

Normal Reference Values

Use these thresholds to define anemia 1:

• Adult males/postmenopausal females: Hb <13.5 g/dL (Hct <40%)
• Menstruating females: Hb <12.0 g/dL (Hct <36%)
• Pregnant women (varies by trimester): Hb <11.0 g/dL in first/third trimester, <10.5 g/dL in second trimester 1

Important note: For Black patients, consider that Hb cutoffs may overdiagnose anemia by 0.8 g/dL (Hct by 2%) compared to White patients, though race-specific cutoffs are not officially recommended. 1

Treatment Algorithm by Clinical Context

For Iron Deficiency Anemia (General Population)

Oral iron supplementation is first-line therapy:

• Adults: 60-120 mg elemental iron daily 2, 1
• Children: 3 mg/kg/day of iron drops 2
• Continue for 2-3 months after hemoglobin normalizes to replenish iron stores 2

Treatment failure criteria: No hemoglobin increase of ≥1 g/dL (or Hct ≥3%) after 4 weeks of compliant oral iron therapy 1

For Pregnant Women

• Start 30 mg/day oral iron at first prenatal visit (primary prevention) 1, 2
• If anemia develops: Increase to 60-120 mg/day 1, 2
• If Hb <9.0 g/dL or Hct <27.0%: Refer to physician for further evaluation 1
• Treatment failure: If no response after 4 weeks, evaluate for thalassemia minor or sickle cell trait in women of African, Mediterranean, or Southeast Asian ancestry 1, 4

For Postpartum Women with Treatment Failure

Switch to intravenous iron if oral therapy fails:

• Ferric carboxymaltose is preferred due to rapid effectiveness and better tolerability 4
• Iron sucrose alternative: 200 mg per dose over 10 minutes 4
• Iron dextran: Up to 20 mg/kg over 6 hours (higher anaphylaxis risk, requires resuscitation facilities) 4
• Monitor for 60 minutes after first IV iron dextran dose; non-dextran formulations also require monitoring 1, 4

For Chronic Kidney Disease (CKD) Patients

Iron deficiency is the primary correctable cause of anemia in CKD:

• Evaluate when Hb falls below stage-specific thresholds: Generally <13.5 g/dL for males, <12.0 g/dL for females 1
• Check iron studies: TSAT and ferritin are best indicators 1
• Intravenous iron is superior to oral iron in CKD, particularly for dialysis patients 1, 5
• Target iron parameters: TSAT >20% and ferritin 100-500 ng/mL before considering ESAs 1

For CKD patients with persistent anemia despite iron repletion:

• Non-dialysis CKD: Consider ESA therapy only if Hb <10.0 g/dL, individualizing based on symptoms and transfusion risk 1
• Dialysis patients (CKD 5D): Start ESA when Hb falls to 9.0-10.0 g/dL to avoid dropping below 9.0 g/dL 1
• Target Hb range with ESA therapy: 11.0-12.0 g/dL (Hct 33-36%) 1
• Never intentionally exceed Hb 13.0 g/dL (Hct 39%) due to increased cardiovascular risk and mortality 1

Critical warning for CKD patients: The Normal Hematocrit Study showed increased non-fatal myocardial infarctions and deaths when targeting normal Hct (42%) versus 30% in hemodialysis patients with cardiac disease. 1 Use ESAs cautiously in patients with active malignancy, history of stroke, or cardiovascular disease. 1

Key Clinical Pitfalls

• Don't rely on Hb/Hct alone: These are late markers that miss early iron deficiency 3
• Hemoglobin is more accurate than hematocrit: Hct is unstable with blood sample storage and falsely elevated in hyperglycemia 1
• Confirm low readings: Repeat testing, especially if using capillary blood (avoid "milking" the finger) 1
• Address underlying causes: Evaluate for occult bleeding, malabsorption, or chronic inflammation if anemia persists despite treatment 4, 2
• In CKD, regular small-dose IV iron prevents functional iron deficiency better than oral supplementation 1, 5