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Background: Blood donation is associated with a number of adverse events. Most of these are both uncommon and non-severe, leading to mild discomfort for the donor at worst. However, adverse events occurring outside of the donation facility have largely not been studied. In this study, we aim to further the understanding by performing the first large-scale analysis of short-term risks following whole blood donation.

Methods: We set up a nationwide cohort of donors who donated whole blood between 1987 and 2018. Analyses were conducted using conditional logistic regression in a self-comparison design, where each donor was compared only to themselves, considering the 30-day risk of 16 outcomes following whole blood donation. Outcomes included cardiac/vascular diseases such as myocardial infarction, unspecified conditions such as fainting, accidents or external causes of injury, and death.

Results: A total of 963,311 donors were included, 19,670 of whom experienced at least one of the outcomes within 30 days of a blood donation. For fainting and hypotonia we observed transient 2 to 5-fold risk increases on the day of donation and the subsequent 2–3 days. Importantly, the risk increase for the most pronounced effect corresponded to less than 1 additional events of fainting per 200,000 blood donations. Risks of all other outcomes were either unaffected or lower than expected right after blood donation.

Discussion: To conclude, we found no evidence of new or unexpected short-term health effects after blood donation and confirmed that risks of hypotension-related events requiring hospital care are present but small.