Blood Test Timing Affects Anaemia Diagnosis
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- Sophie Wehrens at Sanquin Blood Supply Foundation analyzed half a million Dutch donor records from 2013–2023 and found haemoglobin and ferritin levels peak in December and dip in summer months.
- Katja van den Hurk notes warmer temperatures increase blood plasma volume, diluting haemoglobin and ferritin concentrations, which may explain lower readings in June–August.
- Haemoglobin levels follow a daily rhythm, peaking around 10:30am and declining through the evening, with larger fluctuations in men and an earlier peak in people over 45.
- Tami Martino observes these circadian variations align with known age-related shifts in chronobiology, suggesting internal clocks influence blood biomarkers.
- John O’Neill cautions against revising clinical guidelines based solely on this data but stresses clinicians should recognize that timing can affect whether patients meet diagnostic thresholds.
Why it matters: For individuals near anaemia or donation thresholds, a morning test in winter could yield a passing result while an afternoon summer test might classify them as ineligible—altering care or participation without actual health change. This timing effect impacts patient outcomes and donor pool consistency.
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