The Real Reason You Feel Tired After The Flu Shot

The flu is not just an uncomfortable illness, it's also potentially deadly. From late 2019 into early 2020, up to 56 million cases of the flu were reported in the United States, according to the Centers for Disease Control (CDC), with somewhere between 24,000 and 62,000 deaths.

That's why the flu shot is recommended every year by doctors. Inoculation against influenza can prevent you from falling ill with the flu, reduce symptoms if you do catch it, and protect others through herd immunity, according to Bustle.

But you might be wary of side effects of the shot, including the feeling of fatigue that some people report. According to experts, however, it's a normal reaction and, while bothersome, is nothing to fear.

Dr. Gustavo Ferrer of the Cleveland Clinic Florida Cough Center told Bustle that the tiredness some people feel is simply the body's defenses gearing up to protect you. "The symptoms are the result of the antibodies produced by our body in order to build up an immune response. In essence, a foreign substance (dead virus) ​entering our body that our defenses recognize and respond with fatigue, tiredness, low-grade fever, and lousiness," he said. Fatigue should pass within a day or so and should not be harmful.

What else might you feel when you get the flu shot?

According to Dr. Ferrer, resting following the shot is key to fighting the feeling of tiredness. "This is the time to rest. Don't push through. You need time to restore your energy," he said.

Side effects from the flu shot can include things like soreness or redness at the site of injection, fever, headache, muscle aches, and nausea, according to the CDC. For most people, these pass within 24 to 48 hours and don't causes issues. Some people might feel dizzy or faint upon receiving the shot, which is usually a reaction to the injection itself.

A few symptoms might be indicative of an allergic reaction, however, and should be taken seriously. These include problems breathing, wheezing or hoarseness, swelling near the eyes or lips, hives, weakness, paleness, dizziness, and a fast heart rate. If you notice any of these symptoms, call your doctor or, depending on the severity, 911.

The flu shot is safe for pregnant women. People with a rare condition called Guillain-Barré syndrome are not advised to get the flu shot, along with anyone with a severe egg allergy. And if you're feeling ill or under the weather for any reason, postpone the shot until you feel better.