Flu Shot Side Effects Like Fatigue Don't Mean You Have the Flu, But They Do Exist—Here Are the Ones to Know About

During a normal season, the flu affects five to 20 percent of the population. That’s tens of millions of individuals in the United States alone. And the severity of the virus varies—some people will experience mild symptoms, while others die from the flu. According to the World Health Organization, the seasonal flu kills somewhere between 290,000 to 650,000 a year.

While this may sound scary, the good news is the spread of the influenza virus can be slowed. Thanks to the flu shot, protection is possible—and even if you do get the flu, the flu shot typically means symptoms are less severe. In other words, most experts say getting the flu shot is a good idea, especially with the COVID-19 pandemic still around. But it's worth noting that some individuals will experience side effects.

While most flu shot side effects are relatively harmless (if uncomfortable), here's what you should know about potential side effects of the flu shot. Remember, they're not long-lasting, so don't let them discourage you from getting the shot!

Side effects of the flu shot


“As your body is busy building immunity to the virus that has been inserted into it, you may feel a little tired,” Dr. Chun Tang, MD, a physician at Pall Mall Medical, explains. “This is completely normal.” To combat feelings of exhaustion and fatigue, try to get an early night and let your body do its work. You can also take naps, as needed.

Redness or swelling

The most common side effect of the flu shot is a reaction at the injection site, which is typically on the upper arm. "People often experience some injection site reactions like redness and swelling," Dr. Philip Kadaj, MD, a Michigan-based internal medicine specialist, tells Parade.com. And while this may be uncomfortable, it is completely normal. Redness and swelling is a common side effect that usually only lasts a few days and goes away on its own.

Pain at the injection site

Another common side effect is pain at the injection site. Why? Because the flu shot is given intramuscularly. According to the CDC, you have a 10 to 64 percent chance of experiencing some muscle soreness in your upper arm. To combat discomfort, take an over-the-counter pain reliever, like Tylenol, Advil, or Motrin.


Some individuals will experience headaches after receiving the flu shot. In fact, according to the CDC, pain and discomfort is a relatively common reaction. The good news is this reaction is temporary. Individuals usually feel relief within 48 hours or less, and said pain can be treated using over-the-counter products, like acetaminophen and ibuprofen.

Body aches

In addition to headaches and injection site pain, the flu shot can cause body aches. As mentioned, discomfort is a common side effect of the flu vaccine—and all vaccines. As with other aches and pains, body aches can be treated using over-the-counter products.

Related: How to Treat a Common Cold

Low-grade fever

Another common side effect of the flu shot is a low-grade fever or fever of 101°F or less. As with headaches and body aches, this reaction usually resolves itself rather quickly. Your fever should go away within a day or two.

Related: Myths and Facts About the Flu


Some individuals will become nauseous after receiving the flu shot; however, as with headaches, body aches, and a low-grade fever, the CDC notes this is a normal reaction.

Related: What Foods to Eat When You Have the Flu

Flu-like symptoms

In addition to the aforementioned side effects, some individuals will experience flu-like symptoms, including but not limited to malaise, a cough, and/or a runny nose. “Some patients have some ‘flu-like’ symptoms for 24-48 hours afterward,” Kadaj says. “It is basically a sign of the immune system responding to the vaccine and starting the process of developing antibodies.” If these symptoms become troublesome or problematic, over-the-counter medication can be taken. Rest is also helpful.

Related: What Do I Have: A Cold Or the Flu? 

And finally, while unlikely, severe allergic reactions are possible. “Life-threatening allergic reactions to flu shots are very rare,” the CDC explains. “[However,] signs of a serious allergic reaction can include breathing problems, hoarseness or wheezing, hives, paleness, weakness, a fast heartbeat, or dizziness.”

If you experience any of these symptoms, you should contact your physician immediately and/or call 911.

Next up, here are the best ways to prevent the flu.


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