Blood test timing may sway anaemia diagnoses: study — SkimNews
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- Sophie Wehrens at Sanquin Blood Supply Foundation analyzed blood measurements from roughly 500,000 Dutch donors registered between 2013 and 2023, finding haemoglobin and ferritin concentrations vary by both time of day and season.
- Haemoglobin and ferritin levels peaked in December and bottomed out around June–August, a pattern the team links to the body dilating blood plasma volume in response to warmer temperatures.
- Daily haemoglobin levels peaked at approximately 10:30am and gradually fell by evening, with slightly greater daily fluctuation in men than women and a peak about one hour earlier in donors over 45.
- Katja van den Hurk of Sanquin said the timing of a clinic visit or donation appointment may determine whether a person is considered anaemic or ruled ineligible to donate blood.
- John O'Neill at the MRC Laboratory of Molecular Biology cautioned against changing clinical guidelines on the findings alone, but said clinicians should be aware that haemoglobin levels fluctuate.
- Tami Martino at the University of Guelph, who was not involved in the study, called the differences small but potentially decisive for patients whose haemoglobin sits right on a diagnostic or donation threshold.
Why it matters: For the millions of routine blood screenings and donor eligibility checks performed globally each year, this half-million-person dataset suggests the hour of the test — and the season — could move borderline patients into or out of an anaemia diagnosis. The researchers stop short of recommending guideline changes, but the scale of the evidence adds weight to calls for time-of-day awareness in clinical blood work.
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