Blood Donation & Exercise: What You Need to Know

There isn’t much that is more essential to exercise than your blood! Talking simplistically, the more oxygen-rich blood rushing through your body to your screaming muscles, the faster and longer you can keep running!

Giving blood is a truly great, life-saving act. If you do make the decision to donate blood, there are some things you should keep in mind before you go back to full training…

How does giving blood affect your performance?

A 2013 study looked at the short-term effects of donating blood on a cycling endurance test.

Each participant rode to exhaustion on a stationary bike before giving blood, repeating the test two hours, two days, and seven days after the donation.

The study focused on both time to exhaustion and maximum oxygen consumption. VO2 max dropped by 15% and time to exhaustion decreased by 19% during the exercise test two hours after a blood donation.

VO2 max was 7% lower than pre-donation levels at two and seven days post-donation.  

Another study, this time from 2011, suggests that VO2 max returns to normal (pre-test level) three weeks after the date of the donation.

What happens after you donate blood?

Your body has an amazing capacity to replace all the cells and fluids that have been lost. Millions of red cells are made and die every second.

When you give blood, you lose red cells and the body needs to make more to replace them.

Special cells in the kidneys sense that the level of oxygen in the blood has decreased (due to the loss of red cells) and start secreting a protein that passes through the bloodstream until it reaches the bone marrow (the soft fatty tissue inside the bone). 

The bone marrow produces stem cells – the building blocks that the body uses to make the different blood cells – red cells, white cells and platelets.

This protein sends a message to the stem cells telling more of them to develop into red blood cells, rather than white cells or platelets.

Your body makes about 2 million new red cells every second, so it doesn’t take long to build up stores of them again.

Why are red blood cells so important?

There is an important link between your red cells and your health because it’s these cells, in particular, the red-coloured haemoglobin that they contain, that carries the oxygen around your body to your muscles.

Haemoglobin contains iron, some of which is lost with each donation. To compensate, iron is moved from the body’s iron stores, and the body also starts to increase the amount of iron it absorbs from food and drink (men normally have more iron stores than women). 

An iron deficiency can result in reduced haemoglobin levels, and eventually, if not treated, in iron deficiency called anaemia. This deficiency can make you feel fatigued, which will be exaggerated by exercise.

After a donation, most people’s haemoglobin levels are back to normal after 6 to 12 weeks – one of the reasons that blood donation is only allowed a few times per year.

So, blood donation will lead to a notable short-term drop in performance, but the research to date indicates that your body returns to normal after about three weeks, with the worst of the fatigue coming in that first week.

If you can, please do!

Giving blood saves lives. Over 6,000 blood donations are needed every day, and every year approximately 200,000 new donors are needed. It is of course not possible for everybody to be able to give blood – for a number of reasons – so if you are eligible to donate, please consider it!

To find out how/where you can donate blood here in the UK, please visit

Last updated on March 2nd, 2021.


  1. I donate blood when I can and also enjoy triathlons and the training. I only notice the difference in performance when training in the first week to ten days and usually only if I work at the higher end of intensity. I can only describe it as running out of legs! If I maintain an easy pace it’s fine. Basically I try and take two days off or at least easy, but feel this is a small price to pay for the benefits to someone who needs help. It certainly doesn’t require missing weeks of training so there are no excuses!!

  2. Hi, I donate Platelets about six times each year. I am curious after reading your article about Blood Donation impacts on fitness what impact does Platelet Donation have on fitness.

  3. In line with Peter, I donate Platelets and Plasma (about 20 times a year) and yet I am unsure of the impact that Platelet donations has on my endurance etc.

    On a slightly different front, I have heard that that elite athletes avoid blood donations because of the possible impact the insertion of a needle into their arm may have upon their drug testing regime. Admittedly it was something I heard some time ago and I cannot remember the source (whether an elite athlete, a coach or a governing body) when I asked the question and suggested targeting governing bodies.

  4. In line with Peter, I donate platelets and plasma on a regular basis and would be interested in reading any research on the effects of those donations as the actual amount of blood removed is very small (the reason that platelets donations can occur more frequently that whole blood).

    On another front, some time ago I enquired about whether the Donor service was targeting and marketing to elite athletes in any/all sports. The answer I received (and it may not have been the Donor service who gave it) was that the insertion of the needle would/could compromise the drug testing programme that elite athletes find themselves in. Is there any validity to this comment especially as you are suggesting that if people can give, they should.

    I look forward to hearing.