plastic heart-shaped bag filled with blood

What to Know About Donating Blood

Throughout the holiday season, blood donation was likely the last thing on your mind. You’re not alone. Distracted by festivities, colds, flu, and travel, even regular blood donors—people who generously donate up to six times a year—stay away. The result: shortages in January. 

That’s why the first month of the year is National Blood Donor Month. 

We spoke to Eldad Hod, MD, to find out more about the importance, safety, and benefits of donating blood. He oversees all of Columbia’s clinical laboratories, including the blood bank, and recently determined that iron-deficiency caused by donation does not impair donor cognition or quality of life.  

Who can donate blood?  

In general, to donate blood you must: 

  • feel well—after having a cold, flu, or COVID you should wait 14 days after symptoms have resolved 
  • be at least 16 years old
  • weigh at least 110 pounds 
  • not have donated within the past 56 days

Right now, men who have sex with men can donate if they’ve abstained from sexual contact with other men in the past three months. This restriction may be relaxed soon.  

When you donate blood, you answer a short questionnaire with questions about travel (the parasite that causes malaria, for example, can be transmitted through blood and is common in parts of Africa, Asia, and South America), certain behaviors, medical conditions, and medications (some can harm a fetus if transfused into a pregnant woman).  

Then your temperature, blood pressure, heart rate, and hemoglobin are checked. Levels of hemoglobin in the blood are determined by a finger prick; this test makes sure you have enough blood cells to safely donate. Sometimes people think this test measures iron levels, but it is not the same thing.  

Before your study, had blood donor well-being ever been examined? 

It has been known for decades that blood donation makes donors iron-deficient for months following donation.  

There are studies—especially in children and premenopausal women—suggesting that iron deficiency resulting from diet impairs memory and thinking processes and causes fatigue. Iron deficiency at birth has even been associated with lower IQ later in life.  

Nonetheless, no one had ever performed a definitive, double-blind, randomized study examining the effects of iron deficiency caused by blood donation on these domains.  

We partnered with Yaakov Stern, PhD, Christian Habeck, PhD, and Elise Caccappolo, PhD, all at Columbia University Vagelos College of Physicians and Surgeons, to design a battery of state-of-the-art cognitive tests and well-being surveys to assess the impact of blood donor iron deficiency and of iron repletion on a broad range of cognitive outcomes and measures of well-being. 

What was your primary concern about blood donation? 

We were concerned about the donor and the future recipient of the blood. 

We were concerned that a donor’s iron deficiency would impair the donor’s performance on tests of memory and cognitive processing speed (how quickly the brain reacts and makes decisions) and on their well-being. Namely: fatigue. We also examined general health, physical functioning, depression, and anxiety. 

Very old data suggest that red cells from people who are iron-deficient may be of poorer quality. Our study was designed to determine if that is true and whether quality could be improved by restoring iron levels in the donors.   

What did you find?  

Our results show that iron deficiency caused by blood donation does not significantly harm either the donor or the patient getting that blood.  

We found that blood from iron-deficient donors met FDA standards. There are no measurable effects of blood donation-induced iron deficiency on cognitive performance and well-being in adult donors. 

There are some caveats: 

  • The more iron in the blood donor, the more hemoglobin is present in the blood. We still do not know the consequences of receiving blood with a lower dose of hemoglobin.  
  • In women under 50 years old, presumed to be pre-menopausal, there was a statistically significant difference in quality of blood, which requires further study. Iron repletion improved the quality.  
  • We did not study teenage blood donors. These donors may be particularly vulnerable to the effects of iron deficiency, so our results are not applicable to this donor group, which is responsible for about 1 in 10 donations.    

What’s the bottom line for blood donors? 

Go donate blood! Each unit donated can save lives.  

Although blood donation may make you iron-deficient, there is no measurable harm to you, and there is even the potential for blood donation to be good for you: Blood donors tend to be happier, healthier, and live longer. 

Where can I donate blood? 

CUIMC hosts blood drives throughout the year. At other times, the New York Blood Center is the major supplier of blood in the NYC region. Anyone can schedule an appointment to donate at one of their sites. 


Read more: The Surprising Benefits of Donating Blood

Eldad Hod, MD, is vice chair for laboratory medicine; director of the Center for Advanced Laboratory Medicine; and associate professor of pathology & cell biology at Columbia University Vagelos College of Physicians and Surgeons. 

The study, "A randomized trial of blood donor iron repletion on red cell quality for transfusion and donor cognition and well-being," was published Dec. 22, 2022, in the journal Blood.