Signs and Symptoms of Anemia in Adults
Anemia is defined as a hemoglobin concentration below the lower limit of normal: <130 g/L in men over 15 years, <120 g/L in non-pregnant women over 15 years, and <110 g/L in pregnant women in the second and third trimester. 1
Laboratory Findings (Primary Diagnostic Signs)
The most reliable signs of anemia are detected through laboratory testing:
- Reduced hemoglobin (Hb) concentration - the most direct measure of anemia, reflecting decreased functional iron in the body 1
- Reduced hematocrit (Hct) - indicates the proportion of whole blood occupied by red blood cells; falls after hemoglobin drops 1
- Microcytosis (low MCV) - reduced mean cell volume, indicating small red blood cells, particularly in iron deficiency anemia 1
- Hypochromia (low MCH) - reduced mean cell hemoglobin; MCH is probably a more reliable marker than MCV as it's less dependent on storage conditions and is seen in both absolute and functional iron deficiency 1
- Low serum ferritin - the single most useful marker of iron deficiency anemia 1
- Reduced transferrin saturation - helpful when false-normal ferritin is suspected 1
- Elevated red cell distribution width (RDW) - indicates variability in red blood cell size 1
Clinical Symptoms (What Patients Experience)
While laboratory findings confirm anemia, patients may present with:
- Fatigue and weakness - the most common presenting symptoms in chronic anemia 2, 3
- Dyspnea (shortness of breath) - particularly with exertion 2
- Lightheadedness or dizziness 2
- Chest pain or palpitations - especially in more severe cases 2, 3
- Reduced exercise tolerance - inability to sustain physical activity, particularly notable in athletes 3
Important caveat: Many patients with mild to moderate anemia may have no symptoms at all, particularly if the anemia developed gradually 3. This is why laboratory screening is essential in at-risk populations rather than relying on clinical symptoms alone.
Special Considerations for Pregnant Women
In pregnancy, specific hemoglobin thresholds apply:
- Anemia defined as Hb <110 g/L in second and third trimester 1
- Hemoglobin and hematocrit naturally decline during first and second trimesters due to expanding blood volume 1
- Paradoxically, very high hemoglobin (>150 g/L) or hematocrit (>45%) in second/third trimester indicates poor blood volume expansion and is associated with adverse outcomes including preterm delivery, fetal growth retardation, and low birthweight 1
Workup Requirements
When anemia is suspected based on hemoglobin levels, the minimum workup should include 1:
- Complete blood count with red cell indices (MCV, MCH, RDW)
- Reticulocyte count
- Serum ferritin
- Transferrin saturation
- C-reactive protein (CRP) to assess for inflammation
A good response to iron therapy (Hb rise ≥10 g/L within 2 weeks) is highly suggestive of absolute iron deficiency, even if iron studies are equivocal 1. This therapeutic trial can serve as both diagnostic and treatment approach.
Common Pitfalls to Avoid
- Don't rely on symptoms alone - anemia screening requires laboratory confirmation, as symptoms are non-specific and may be absent 1, 3
- Serum ferritin can be falsely normal in the presence of inflammation or chronic disease, as it's an acute phase reactant; consider transferrin saturation in these cases 1
- MCV and MCH lose sensitivity for iron deficiency in the presence of chronic disease, thalassemia, or vitamin B12/folate deficiency 1
- In pregnant women, don't assume high hemoglobin is desirable - values >150 g/L warrant evaluation for pregnancy complications 1