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Want to donate blood more often? It doesn't have any major side effects

A major randomised trial could have an impact worldwide.

Image: Shutterstock/Azami Adiputera

IF YOU DONATE blood, but want to do so more often, a new study says it shouldn’t have any major side effects.

The first-ever randomised trial of blood donation involving more than 45,000 people in England has just been published in The Lancet. It shows that giving blood more frequently – up to every eight weeks for men and every 12 weeks for women – has no major side effects and could help to increase blood stocks.

In the UK, men can donate every 12 weeks, and women every 16 weeks, but the study showed that reducing the interval between donations by four weeks (to every eight weeks for men, and every 12 weeks for women) had no major impact on the donors’ quality of life, mental function or physical activity. It also increased the amount of blood collected over two years by 33% (1.7 units) in men and 24% (0.85 units) in women.

In Ireland, you can donate blood every 90 days (around three months or 12 weeks) if you are eligible.

The study did find, however, that some people who gave blood more frequently did report minor symptoms including tiredness and restless legs. The research suggests this may have been due to giving blood.

Blood stocks

The report’s authors say the findings may help overcome potential risks to blood stocks, including issues attracting and retaining young donors, and increased demand caused by ageing populations.

In addition, they say it could help to increase stocks of much-needed universal blood groups and rarer blood groups.

As well as people needing occasional blood transfusions, this could help people who need regular blood transfusions, such as people with sickle cell disease.

Lead author, Dr Emanuele Di Angelantonio, University of Cambridge, UK, says: “The study also showed that donors who weighed above average and those with higher initial stores of iron were able to give more blood.”

Up until now, there has been no randomised trial to evaluate the most suitable interval between donations. This has led to varied blood donation policies globally – men and women can donate every eight weeks in the USA, and in France and Germany men can donate every eight weeks and women every 12 weeks.


The study involved 45,042 blood donors (22,357 men and 22,685 women) aged 18 years or over from 25 centres in England. Men were split into three groups to give blood every 12, 10 or 8 weeks, and women gave blood every 16, 14 or 12 weeks. The trial took place over two years.

All participants completed online health questionnaires at the start and end of the trial, and at six, 12 and 18 months to measure quality of life, symptoms related to blood donation (such as tiredness, breathlessness, feeling faint, dizziness, and restless legs), physical activity levels and cognitive function.

They also gave blood samples at the start and end of the trial to measure haemoglobin and iron levels, and the researchers tracked instances where blood donations were postponed due to haemoglobin levels being too low.

Overall, men and women who gave blood most frequently donated 33% and 24% more blood than people who gave blood least frequently. Over two years, men and women in the most frequent donation groups gave 6.9 units and 4.3 units of blood on average each. This is compared to 5.2 and 3.4 units for men and women in the least frequent donation groups.

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There was no difference in serious adverse events, quality of life, cognitive function or levels of physical activity between people who gave blood most and least frequently.


However, people who gave blood more frequently reported more symptoms potentially related to blood donation than those who gave blood less frequently. These symptoms included feeling faint, tired, breathless, and dizzy, and were more commonly experienced by men than women. Men also had palpitations and restless legs more often than women.

On average, compared to people who gave blood less frequently, people who gave blood most frequently had lower iron levels and were more likely to be iron deficient by the end of the trial – 24% (598 of 2525) of men who gave blood most frequently, compared to 12% (359 of 2952) of men who gave least frequently, and 27% (655 of 2419) of women who gave blood most frequently, compared to 22% (558 of 2572) of women who gave least frequently.

People giving blood most frequently also had lower haemoglobin levels after two years and were more likely to have haemoglobin levels below the minimum threshold to donate blood.

As a result, during the two years of the trial around one in three people giving blood most frequently had their donation postponed at least once due to their haemoglobin levels being too low.

However, the researchers found that the reduced levels of haemoglobin and iron did not fully explain the increased rate of symptoms experienced by those giving blood most frequently, and propose that more research be done to better understand the causes of these symptoms.

Read: Lifetime ban on gay men donating blood lifted>

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