When Is Fever After Surgery a Concern?

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A fever after surgery (postoperative fever) is a common complication. There are a range of reasons why you might get a fever after surgery, including problems like infections that need treatment. You might be more likely to have a post-op fever after a major surgery or procedure because your body is under a lot of stress and there is more tissue trauma and inflammation. Both children and adults can get fevers after surgery.

causes of fever after surgery
Verywell / Emily Roberts

Most postoperative fevers are not serious and can be treated at home with Advil (ibuprofen) or Tylenol (acetaminophen). Some low-grade fevers do not need treatment at all and will get better on their own. However, a fever after surgery can also be a sign of a more serious complication like an infection. That’s why any fever after surgery needs to be taken seriously and watched closely. 

This article explains some of the reasons you could have a fever after surgery. It also discusses how to treat a postoperative fever and when to call your provider if you have a fever after surgery. 

Causes of Fever After Surgery

Surgery-related fevers can have different causes.

Lung Problems

Two post-surgery complications that can cause fever include atelectasis and pneumonia.

A partial or completely collapsed lung (atelectasis) is one of the most common causes of fever after surgery. Anesthesia causes the little air sacs (alveoli) within your lungs to deflate, leading to areas of the lung collapsing.

Pneumonia is a lung infection that inflames the air sacs and may fill them with fluid or pus. The infection can come from bacteria, viruses, and fungi, or can be caused by inhaling (aspirating) food or liquid. Sometimes, this can happen while a person is having surgery or right after when they are recovering.

Urinary Tract Infection (UTI)

A urinary tract infection (UTI) can cause a fever post-surgery. If you had a urinary catheter during your surgery, you have a higher chance of getting a UTI.

Other Infections

There are also other infections that could cause a fever after surgery

  • An infected wound or abscess
  • An infected surgical incision or central line site
  • Septicemia (an infection that reaches the blood)
  • Peritonitis (an infection in the abdomen caused by a leak at the surgical site)

Blood Clots

A low-grade fever is sometimes seen in patients with blood clots after surgery. However, they will also usually have other symptoms of a blood clot like pain and shortness of breath.

Types of blood clots that can happen after surgery include:

  • Deep vein thrombosis (DVT) is a blood clot that forms in a vein, usually the leg. If you are not moving as much as usual after surgery, DVTs are more likely to form.
  • pulmonary embolism is another type of blood clot that gets lodged in the lungs. 

Medication Reaction

Post-surgery fevers can be caused by blood transfusions or medications that were given during surgery. Fevers caused by a medication reaction may get better on their own. When they do not go away or get worse, fevers can be a sign of a more serious reaction.

Non-Surgical Causes

Sometimes, the surgery itself is not the cause of a postoperative fever. You could have caught the flu a few days after surgery or you might have an infection that isn’t related to the procedure. 

The more time that passes between the day of your surgery and the day of your fever, the less likely it is that the fever is related to your surgery. This is especially true if you are weeks into your recovery when you get a fever. 

Common non-surgical causes of fever include:

  • Viruses (such as the flu or a cold)
  • Strep throat (a bacterial infection)
  • Neurological ​fever caused by a brain injury
  • Other infections

Types of Postoperative Fevers

You may have different types of fevers after surgery, based on how high your temperature is. You also might start out with one type of fever that progresses to a more serious type. 

Low-Grade Fever

A fever is considered low-grade if your temperature is one or two degrees above the normal reading of 98.6 degrees F. While it might not be a serious fever, it’s still best to let your healthcare provider know if you have a low-grade fever after surgery. 

A fever of 99 F is very common, especially in the first week while your incision is healing. If you have a fever and your incision is not healing well, tell your provider right away. You may need medical attention.

You should also let your healthcare provider know if you have a low-grade fever that does not go away after a few days.

Moderate Fever

A fever between 100.6 F and 102 F is considered moderate. If you have a moderate fever after surgery along with the following symptoms, your provider might want to see you as soon as possible or send you to urgent care or the ER:

  • Nausea
  • Vomiting
  • Unexplained increase in pain
  • Disorientation or confusion
  • Pus or drainage from your incision
  • Redness near your incision
  • Shortness of breath

These symptoms can be a sign that a post-surgery problem is developing.

You should also get medical care if your fever does not come down within an hour of taking a dose of Advil or Tylenol.

High Fever

A fever higher than 102 F in adults needs immediate medical attention. A fever this high could mean you have a serious infection, there is a problem with your surgical site, or you are having a serious reaction to a medication.

Tell your provider if you have a high fever, then go to urgent care or the ER. 

Treatment for Post-Operative Fever

A low-grade fever may not need treatment other than over-the-counter (OTC) medications such as Tylenol or Advil. These medications are usually effective for treating a fever.

If you are taking pain medication that contains Tylenol or Advil after surgery, know that you could have a fever and not realize it. These medications typically lower fever and treat pain at the same time.

Bringing down a fever with medication may not be enough. You may have an infection that requires prescription antibiotics or need wound care.

An antibiotic will not always be able to treat a fever. For example, antibiotics do not treat an infection caused by a virus or fungus. It’s also possible that an infection is not the cause of a post-surgery spike in temperature.

If you have a high fever, your provider may do blood, urine, and wound cultures. These tests can help determine which bacteria or other organisms are causing infection and make the best choice for treatment. 

Your provider might want you to start treatment before your test results come back. Alternatively, they also may have you wait until the test shows what the cause of the infection is before making a decision about treatment.

In some cases, your surgeon might want you to start taking antibiotics before surgery or right after, even if you do not have any signs of an infection, as a preventive measure. 

How to Prevent Fever After Surgery

There are some steps you can take after surgery to prevent an infection:

  • Check your incision daily until it is healed.
  • Wash your hands before and after touching your incision.
  • Drink lots of water to stay hydrated and help avoid a urinary tract infection (UTI). 
  • Do proper incision care and dressing changes.
  • When you’re physically able and approved by your healthcare team, start moving around and increasing your activity levels. 

When to Call a Healthcare Provider

Call your provider if you have a fever after surgery, even if it’s not very high. While they might tell you that it’s nothing to worry about, they will probably want you to keep an eye on it and let them know if it’s not getting better. They’ll also want to know if you start having any other symptoms (like a pus-filled discharge from your incisions or increased swelling) that could point to a post-op problem like an infection.

Summary

It is very common to have a mild fever after surgery. If you have a fever between 99 F and 101 F, it may go away on its own or with OTC medication. However, you should still tell your provider you have a fever and check it to make sure it’s not getting worse. 

A fever can be a sign that you're developing an infection somewhere in your body. If your fever is high or not getting better, your provider might need to do tests to figure out the cause and recommend treatment. 

Having a fever over 102 F needs medical attention. You should also go to urgent care or the ER if you have nausea, vomiting, shortness of breath, disorientation, or any signs of wound infection after surgery. 

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.