Caffeine may undermine blood transfusion effectiveness

Medical Xpress / CU Anschutz Medical Campus / Haematologica ^ | Sept. 4, 2025 | Kelsea Pieters / Monika Dzieciatkowska et al

[ConservativeMind]

A new study has found that caffeine, the world's most consumed psychoactive substances, may impair the quality of donated blood and reduce the effectiveness of transfusions—especially in recipients whose red blood cell (RBC) metabolism is influenced by a common genetic variant.

The REDS RBC-Omics study, which analyzed samples from over 13,000 blood donors, the study reveals higher levels of caffeine in the blood are linked to RBCs that are more prone to damage during storage and less effective after transfusion. In a clinical setting, transfusions of RBCs with relatively high levels of caffeine resulted in lower increases in patients' hemoglobin levels and greater signs of RBC breakdown (hemolysis).

These negative effects were especially pronounced in transfusion recipients and blood donors carrying common variants in the ADORA2b gene, which regulates how RBCs function under low-oxygen conditions.

"The translational implications of our findings are significant," said D'Alessandro. "First, donor caffeine consumption, a common dietary exposure for up to 75% of Americans, emerges as a modifiable behavioral factor potentially influencing RBC storage quality and transfusion outcomes.

"Given caffeine's short biological half-life, transient dietary modifications around the time of blood donation might mitigate its negative impact, aligning with blood donation guidelines in several European countries where donors are advised to limit caffeine intake prior to donation.

"Conversely, in other regions, such as the United States or Italy, caffeine consumption before blood donation is not actively discouraged and may even be implicitly encouraged due to its known beneficial acute effects on blood pressure, potentially expediting the donation process and reducing vasovagal reactions.

"Indeed, moderate caffeine intake can transiently increase donor blood pressure and vascular tone, facilitating venous access and blood withdrawal efficiency. However, this advantage must be balanced against caffeine's mild diuretic properties, which may predispose donors to dehydration—an established risk-factor for adverse donation-related events."

---

TOPICS: Health/Medicine
KEYWORDS:

[ConservativeMind]

If you most want to help the recipient of your donated blood, don’t have caffeine for some number of hours before giving.

The half-life of caffeine is 3-6 hours.

[ConservativeMind]

The “Take Charge Of Your Health” Ping List
This high volume ping list is for health articles and studies which describe something you or your doctor, when informed, may be able to immediately implement for your benefit.

Email me to get on either the “Common/Top Issues” (20 - 25% fewer pings) or “Everything” list.

[yesthatjallen]

So coffee is bad again? I keep losing track.

[exnavy]

Blood transfusions are bad, they thin your caffene.