What Is a Low-Grade Fever? We Asked Experts to Explain

Learn what a low-grade fever is and what to do if you have one.

The COVID-19 pandemic may have made you wary of every body temperature change you notice—whether that's experiencing cold sweats or feeling a little warmer than usual.

It's with good reason, of course: fever is a symptom of the coronavirus, per the Centers for Disease Control and Prevention (CDC), and shouldn't be taken lightly. It's also a flu symptom.

But not all fevers are created equal. While the most severe ones happen above 103 degrees Fahrenheit and may warrant medical attention, others, like what some experts call "low-grade fevers" can be a bit harder to identify. Here's what you need to know if your temperature is reading a little higher than usual.

What Is a Low-Grade Fever?

First, let's define what a fever is: Per the CDC, a person has a fever if their temperature is at or above 100.4 degrees Fahrenheit (38 degrees Celsius). And though it doesn't necessarily feel good, a fever can be a positive clue to your health: It's actually a sign that your body is working to fight off an illness or infection, and working to get you healthy again.

For most people, a "normal" body temperature falls somewhere around 98.6 degrees Fahrenheit, according to MedlinePlus. However, not everyone's body temperature is exactly 98.6 degrees Fahrenheit, and a normal range can be defined as from 97 degrees Fahrenheit to 99 degrees Fahrenheit.

But the definition of "low-grade" fever isn't as clear-cut as a normal body temperature or fever. "Low-grade fever doesn't have a real medical definition," Donald Ford, MD, a family medicine physician at Cleveland Clinic, told Health.

Alka Gupta, MD, an assistant professor of medicine at Weill Cornell Medicine added that "there is no widely accepted range for low-grade fever." Dr. Gupta told Health she's seen low-grade fever categorized as anything between 99 degrees Fahrenheit to 100.4 degrees Fahrenheit to even smaller windows such as between 100 degrees Fahrenheit to 100.4 degrees Fahrenheit.

In general, since a normal body temperature might fall anywhere from 97 to 99 degrees Fahrenheit, and a "fever" is technically anything 100.4 degrees Fahrenheit or higher, a "low-grade fever" could be defined as anything in that space between a normal temperature and a fever.

What Can Cause a Low-Grade Fever?

While it might be tempting to think of a low-grade fever as a lesser infection—than one, for instance, that caused a high fever—that's not really accurate. According to the CDC, colds and the flu can cause fevers, along with a host of other issues, and the severity of a fever doesn't depend on the severity of an infection.

The reasoning? Because normal body temperature varies so much from person to person, so do fever temperatures. If a person's normal body temperature is typically lower, the jump of their fever temperature may also be lower, possibly only registering as a low-grade fever, according to a 2021 study published in PLOS ONE.

Older people may also be more susceptible to low-grade fevers than young adults and children, Ramiro Jervis, MD, an internal medicine doctor at the Family Health Centers at NYU Langone, told Health. So, the older you get, the less likely you may be to suffer from a true fever.

That's because sometimes normal body temperature—and, ultimately, fevered body temperature—may drop with age, according to a 2019 review published in Open Forum Infectious Diseases.

What Should I Do if I Have a Low-Grade Fever?

For starters, the only true way to know if you have a fever—low-grade or otherwise—is to take your temperature, so that's your first step.

"It's helpful [for a healthcare provider] to have an actual reading," Dr. Jervis said. The reality is that, if you tell your healthcare provider you "think" you've had a fever for a few days, but you don't have a number or range to back up that claim, that info won't really tell your healthcare provider much about your health.

You shouldn't just take your temperature once and quit. Instead, take it regularly if you feel like something's off. "Check it periodically," Dr. Gupta said. This is helpful because one's body temperature can fluctuate throughout the day and throughout their menstrual cycle.

Knowing whether or not your temperature is consistently high, versus just higher at certain points in the day, will help your healthcare provider get to the bottom of what, if anything, is wrong.

Lastly, don't rush to your healthcare provider if you have a fever, low-grade or not, and no other symptoms, without calling ahead to see what they think you should do, Dr. Jervis advised. If fever is the only symptom you have, you and your healthcare provider might be able to work out a treatment plan via a telehealth appointment, which saves you an office visit.

That said, if you are experiencing more severe symptoms, such as difficulty breathing, in addition to a fever spike, you shouldn't hesitate to visit an emergency room or urgent care clinic.

The good news is that there are various ways to bring your temperature back down if it spikes. For instance, staying hydrated can help your body regulate its temperature, Dr. Ford said. Taking medications with anti-inflammatory properties, such as ibuprofen, can also help, as can cooling off if you're in an especially hot environment, Dr. Ford added.

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