There’s not much that’s more essential to your running (and your life) than your blood.

The more oxygen-carrying power your blood has, the faster you can run.

Without enough oxygen, your body is quickly plunged into acidosis, the deep burning sensation in your legs that you feel at the end of a race or a hard workout.

That is why keeping your iron levels high enough is critical to running well.

Doing anything that would decrease your body’s oxygen-carrying potential would be crazy right?

Well, maybe not if it can save somebody’s life.

Donating blood is an admirable endeavor—according to the American Red Cross, over 41,000 blood donations are required every day in the United States, and given the short shelf life of whole blood and plasma, there’s a constant need for blood.

Though blood donation is lifesaving, runners are often hesitant to give blood because we wonder will giving blood affect your running?

Today we are going to look at how much does giving blood or plasma affect your running performance.

If you are wondering about running before giving blood, we will explain the pros and cons, and give you some guidelines about blood donation recovery time. Finally, we are going to show you 4 ways to limit the negative effects and explain how to recover from giving blood faster.

Can you run after giving blood? Let’s find out.

Running After Donating Blood

A 2013 study by David Hill, Jakob Vingren, and Samatha Burdette examined the short-term effects of donating blood and plasma on a cycling endurance test in nineteen test subjects.

Each subject underwent a ride to exhaustion on a stationary bike before giving blood or plasma, and again two hours, two days, and seven days after the donation.

The researchers measured both time to exhaustion and maximum oxygen consumption, or VO2 max, during each of the four tests.

Unsurprisingly:

They found that both VO2 max and time to exhaustion were negatively impacted in the immediate aftermath of a whole blood donation.

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 still 10% and 7% lower than pre-donation levels at two and seven days post-donation, respectively.

The results of plasma donation are more interesting:

Although the plasma donation resulted in no change in VO2 max at any point, time to exhaustion was decreased two hours post-donation, but not two days or one week out.

Hill et al. hypothesized that this was because the drop in overall blood volume from the plasma loss interfered with anaerobic capacity.

Plasma volume is restored rather quickly, which explains why this phenomenon was not seen two days or a week later.

Now:

Hill et al. showed that whole blood donation still impaired performance a week after giving blood, but how long do the effects linger?

How Long Will Giving Blood Affect Your Running?

This issue was addressed by a 2011 study by T.B. Judd and other researchers at the University of Saskatchewan in Canada, who studied 12 subjects’ VO2 max before a blood donation and once every week for a month following the donation.

Like the previous study, Judd et al. found a marked decrease in VO2 max the day after blood donation.

Over the following weeks, the subjects’ VO2 max gradually returned to normal, reaching its pre-test value three weeks out from the date of the blood donation.

The one drawback to the above studies is that they used only moderately active people from the general population, not trained athletes.

It get’s worse:

A well-trained runner might experience a greater drop in fitness with loss of blood.

A 1995 study examined well-trained cyclists who gave blood, but only followed them for one week post-donation, with findings mostly in line with the previous studies.

Aside from this, there’s no long-term research in whether blood donation more seriously hampers a well-trained athlete.

Can I Give Blood If My Iron Is Low?

There’s one more issue with blood donation that deserves to be mentioned, and that’s iron levels.

When you donate blood, your body replaces the lost red blood cells by synthesizing new ones, a process which consumes iron stored in the form of ferritin.

A rigorous analysis of almost 3,000 blood donors by Clement Finch and other researchers at the University of Washington found that your body’s iron levels (as measured by serum ferritin) are negatively correlated with how often you give blood.

Consider this:

Researcher Dr Pamela Hinton talked about what level runners need to keep their iron levels at, and therefore donating blood as a runner with low iron is a serious risk.

Frequent blood donors are much more likely to be anemic, and this relationship is especially true in women.

Even among the general population, donating blood more than once every 8-12 months can lead to a high incidence of low ferritin levels in women.

Now:

Men can donate more often, but if they exceed three blood donations per year, they too run the risk of having low ferritin, which has a negative impact on your ability to train and race.

The authors suggest that increasing the amount of iron in your diet could help counteract this effect.

When is the Best Time to Give Blood as a Runner?

A good time to donate is during the recovery time after your goal race when your body isn’t under the constant demands of a marathon training schedule or an intense training cycle.

Plan the donation around a rest day and follow with several days of short, easy effort workouts until you begin to feel 100%.

In the 4-5 days following your donation, throw out your watch!

Here’s why:

Your times are going to be slower (the research shows it) so just forget about pace and put some time on your feet.

Remember:

Stay hydrated and eat well before and after the donation. This will help you recover faster from the donation itself.

Giving Blood and Running: Should A Runner Donate Blood?

What’s the bottom line?

There will be a notable drop in your performance, but the research to date indicates that your body returns to normal after about three weeks.

Recovery from plasma donation is even quicker—less than two days and you’re already back to pre-donation fitness.

There’s still more research needed on whether blood donation has an especially large impact on well-trained athletes, as is the case with some other performance inhibitors (like altitude), but if you don’t have any races for the next month, and you’re okay with your workouts being a bit slower for a few weeks, go ahead and donate blood.

But make sure you consider this:

If you donate often, make sure you have your ferritin checked to be sure it’s not too low, especially if you have a history of low iron or anemia.