Blood Donation and Training – How Performance is Affected

Summary: Donating blood saves lives – but as an athlete, you also want to know how a blood donation affects training and performance. This article reviews what research shows about the effects on blood volume, heart rate, and hemoglobin after a typical whole blood donation and how long it may take before you return to peak condition. The main question is how significant the impact on performance is and how best to plan around donation before training and competition. The conclusion is that you can continue to train, but the first few days often involve a noticeable decrease in capacity – and peak performance can be affected for several weeks, making planning for important races extra crucial.

Why Blood Donation is Important – and What Athletes Should Know

Being a blood donor is seriously Awesome and something we encourage. On average, we use 438,000 units of blood each year, but since 2016 donations have been around 407,000-420,000 units, which means we're running at a deficit.

As an athlete, it's important to know how your capacity is affected by donating blood. Here, we dive into the area, check out the research, and see what the numbers actually look like.

Background 

In a typical blood donation, you donate 450 milliliters (ml) of blood. This amount is fairly standardized and also the one tested in studies. First, we go through an intervention study where researchers tested eight male athletes (27 years, 74 kg) with a maximal oxygen uptake (VO2max) of 56 ml·kg−1·min−1. The subjects donated blood and then performed a cycling test at 60% of VO2max in 35-degree heat according to the following schedule:

• 2 days before donation
• 2 hours after donation
• 2 days after donation
• 7 days after donation

The amount given (450 ml) reduced the participants' total blood volume in the body by 9%. But what happened in terms of performance?

Results – Immediate Effect on Temperature and Heart Rate

Two hours after the blood donation — and just before the cycling tests began — two-thirds of the plasma volume had been endogenously restored, meaning the body had naturally increased the plasma volume again. At this measurement point, body temperature was 0.4 degrees higher than the baseline, resulting in participants having an elevated body temperature of 39 degrees just one hour into the cycling test. Skin temperature and sweat rate (1.15 liters per hour) were the same as during the measurement two days before the blood donation.

Blood Volume – Plasma Returns Quickly, But Not Everything

The body is quick to restore blood volume, primarily by replenishing plasma — the water portion of the blood. As mentioned, blood volume was reduced by 9% from the 450 ml blood donation, but within the first two hours, the body restored 163 ml, bringing the blood volume at the start of the test to just 5.8% below the baseline.

But 5.8% lower volume still matters. Since the amount of red blood cells is lower (−287 ml) but the muscles' oxygen demand remains unchanged, the heart must beat faster to circulate enough blood. At the 2-hour measurement, the heart rate was on average increased by 12 beats/min. Twelve beats are not easily dismissed — it's noticeable and significantly reduces performance.

After two days, most was restored except for cardiac output (the volume of blood pumped per minute), which was increased by 6%. This correlated with decreased levels of hemoglobin in the blood: more blood must be pumped per minute to oxygenate the muscles. Here, we can confirm that plasma volume was back to baseline, but the capacity to carry oxygen (hemoglobin levels (Hb value)) was still impaired.

Hb and Oxygen Transport – How Long Are You Affected?

To make it more relevant, we focus on Hb. You can read more about it here.

Two days after the blood donation, the Hb value was down to 142 g/L from the starting value of 153 g/L, a decrease of 7.2%. After seven days, the value was up to 145 g/L, which is still 4.6% below the starting value but on the way back. Unfortunately, the study did not measure beyond this, but looking at the numbers, this implies a recovery of about 1 g/L per day. To regain the starting value of 153 g/L would therefore require approximately an additional seven days, resulting in about 14 days total to reach the original Hb value — assuming hemoglobin synthesis occurs at a constant rate throughout the period.

Recommendations from Swedish Blood Centers

GeBlod, the joint communication center of the Swedish blood centers, answers a common question in their "frequently asked questions" (FAQ). The answer is:

Q: “I run about 5 times a week. How does blood donation affect fitness?

A: Only after 3–4 weeks does the Hb concentration reach the same level as before donation (even with well-stocked iron stores), in cases of latent iron deficiency it takes longer. If you want to perform at your maximum in an endurance-demanding activity, you should not donate blood in the preceding 3–4 weeks.”

The emphasis is on “perform at your maximum”: your absolute peak performance may be impaired during that period, even if your ability to conduct training in good volume is not necessarily destroyed. The advice from GeBlod is based on research done in the field.

Plasma or Whole Blood – Major Difference for Performance

When you donate blood, you can donate whole blood—meaning it contains red blood cells, plasma, and more. In some places, you can also donate just plasma. When donating plasma, you retain your red blood cells and thus your Hb value. If you donate plasma, you are usually back in form within 1, maximum 2 days.

Immediately after donating blood plasma, your capacity is reduced. But it's mostly your own fault if you plan plasma donation on the same day or the day before a race. 😀

Summary – How to Plan Around Training and Competition

We encourage everyone who can and is eligible to donate blood to actually do it. However, expect it to take about a month before you're back to 100%. This doesn't mean you can't train — it's just that you won't reach your absolute peak during this time.

Practical Advice for the Training Week After Donation

Of course, you can run intervals, thresholds, and train at race pace, but be aware that your heart rate won't be entirely reliable compared to previous values.

The conclusion from a major 2017 review is that your capacity is noticeably reduced during the first two days after donating blood, so try to schedule lighter training and/or rest days then. After that, it's pretty much okay to continue training, even in the heat, but be aware that you won't reach the final percentage of your capacity — but you know why, and the capacity will soon return.

So, as you start preparing according to our competition-ready article, make sure not to schedule a blood donation during those 4–5 weeks. Deal.