Is It Safe to Exercise After Donating Blood?

Pushing yourself too hard after a blood donation can make you feel dizzy and could lead to fainting.
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Blood donation is one of the most important ways to share your good health with others. Each unit of blood you donate can help up to three people in need of blood or blood products, according to the American Red Cross.

But doing say may spark some questions about your daily routine. For example: Is it safe to work out after giving blood?

Rest assured that America's blood centers and hospital collection sites want you to have a safe donation experience, and that includes the hours and days after you give blood.

In light of the coronavirus pandemic, is raising awareness about the urgent need for people to donate blood with our Give Blood, Give Back series.

The Risks of Working Out After Giving Blood

Even if you're eager to get back to the gym, don't rush it. AABB and the Mayo Clinic advise blood donors to wait five hours before engaging in any strenuous physical activity or heavy lifting. Other donation sites suggest that you avoid exercise post-donation for 12 to 24 hours.

The primary concern is the risk of fainting due to loss of blood volume, explains Jed Gorlin, MD, MBA, medical director of Memorial Blood Centers and Nebraska Community Blood Bank, divisions of Innovative Blood Resources in St. Paul, Minnesota. If you feel woozy after giving blood in the gym, you could fall and hit your head. Or, if you go for a run at a nearby park and then get back in your hot car, there's a risk that you may faint while driving.

When you donate a single unit of whole blood, you typically lose roughly 10 percent of your total blood volume, according to the National Academy of Sports Medicine. More than half of that blood is the liquid portion, called plasma, according to the Red Cross.

The fluid portion of your blood is replaced very quickly, typically within a day. "Probably within eight hours but certainly within 24 hours, your body has re-equilibrated its blood volume, you had enough to drink, you slowed your urine production — your fluid is back in balance," Dr. Gorlin tells

The remaining portion — red and white blood cells and platelets — consists of solids, also called formed elements. Hemoglobin, an iron-rich protein in red blood cells, carries oxygen from your lungs to the tissues in your body, according to UCSF Health. Complete replenishment of your red blood cells takes more time, about four to six weeks, per the Red Cross.

But there's another post-donation exercise risk that people don't talk about as much. You want the puncture wound where the needle entered your arm to seal over.

Exercise that involves your arms, like lifting weights or tennis, "can pop that little clot right out," Dr. Gorlin says. If that happens, you may bleed under the skin and develop a flat bruise, called a contusion, or a raised bump, called a hematoma. "You could have a sore arm for days," he says.

Exercise With Caution

While strenuous activity should be avoided, you don't have to sit on the couch all day. After you've had a chance to drink some fluids — the American Red Cross recommends drinking an extra 32 ounces — it's generally safe to enjoy some light to moderate activity if you feel up to it, such as a brisk walk or a casual bike ride. Drinking plenty of liquids before and after your donation helps you avoid dehydration.

Recommendations about exercise after blood donation may vary, depending on the type of donation you're making. For example, if you're making a double red cell donation — donating twice the usual amount of red blood cells — you might be advised to avoid strenuous exercise for longer than just a day.

If you feel dizzy or lightheaded during or after post-donation exercise, sit or lie down until you feel better. Make sure you're drinking plenty of fluids and contact your donation center or health care provider if you are concerned about any symptoms you experience after blood donation.

Additional reporting by Christine St. Laurent

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