Fever In Adults: Characteristics, Types, And When It's Serious

Maybe your like

HealthlineSubscribeHow to Tell When a Fever in Adults Is Serious

Medically reviewed by Alana Biggers, M.D., MPH — Written by Noreen Iftikhar, MD on September 17, 2019

Characteristics
Types
When it's serious
Causes
Treatments
When to go to the ER
Takeaway

You may need to get plenty of rest and drink fluids to help your body heal. But if you have a high or long-lasting fever longer than 3 days, you may need urgent medical care.

A fever is a common side effect of illness like the flu. It happens when there is a temporary rise in body temperature. A fever is usually a sign that your immune system is busy fighting an infection or other illness.

In babies and toddlers even a slight fever may be a sign of a serious illness. In adults a fever is not usually serious or life-threatening.

However, sometimes a fever in adults can be a warning signal that something is not right. A high or persistent fever might be a sign of a serious health condition.

What is a fever?

A fever is normally a short-term rise in temperature that helps your body get rid of illness. A fever begins when your immune system makes more white blood cells to fight an infection. The increase in white blood cells triggers your brain to heat your body up.

This causes a fever. In response, your body tries to cool itself off by tightening up on blood flow to your skin and contracting muscles. This makes you shiver and may cause muscle aches.

Your normal body temperature ranges from 97°F to 99°F (36.1°C to 37.2°C). You may have a fever if your temperature rises above this.

Types of fevers

Adults typically have a fever if their body temperature increases to 100.4°F (38°C). This is called a low grade fever. A high grade fever happens when your body temperature is 103°F (39.4°C) or above.

Most fevers usually go away by themselves after 1 to 3 days. A persistent or recurrent fever may last or keep coming back for up to 14 days.

A fever that lasts longer than normal may be serious even if it is only a slight fever. This is because a recurrent fever might be a sign of a more serious infection or health condition.

Common fever symptoms in adults include:

sweating
chills (shivering)
headaches
muscle pain
loss of appetite
fatigue
weakness

When is a fever serious?

Call your doctor immediately if you have a high grade fever — when your temperature is 103°F (39.4°C) or higher. Get medical help if you have any kind of fever for more than three days. Let your doctor know if your symptoms get worse or if you have any new symptoms.

Serious symptoms
A fever may be a sign of serious illness if you have:
a severe headache
dizziness
sensitivity to bright light
stiff neck or neck pain
skin rash
difficulty breathing
frequent vomiting
dehydration
stomach pain
muscle cramps
confusion
seizures
Other signs that a fever may be serious are:
pain when urinating
not urinating enough
passing dark urine
passing urine that smells bad

Causes of serious fevers

If you have serious fever symptoms, let your doctor know if you have recently traveled to a different country or attended an event that had lot of people. This may help your doctor find out the cause.

Common causes of a fever in adults are:

viral infection (like the flu or a cold)
bacterial infection
fungal infection
food poisoning
heat exhaustion
serious sunburn
inflammation (from conditions like rheumatoid arthritis)
a tumor
blood clots

Some adults may have a higher risk of getting a fever. If you have a chronic health condition or have been treated for a severe illness, you may be more likely to get a serious fever.

Let your doctor know about any fever symptoms if you have:

asthma
rheumatoid arthritis
diabetes
Crohn’s disease
heart disease
sickle cell disease
liver disease
kidney disease
chronic lung disease
cystic fibrosis
cerebral palsy
stroke
multiple sclerosis
muscular dystrophy
HIV or AIDS

Some medications and treatments can also lead to a serious fever, these include:

antibiotics
blood pressure drugs
seizure medications
DTaP vaccine
pneumococcal vaccine
steroids
chemotherapy
radiation treatment
methotrexate
azathioprine
cyclophosphamide
post-transplant medications

Treatments

A fever is not normally harmful on its own. Most fevers go away within a few hours to days as your body defeats an infection.

Help yourself feel better with these at-home flu remedies:

stay hydrated by drinking plenty of fluids, such as:
- water
- juice
- soup
- broth
eat light foods that are easy on the stomach
rest
use a cool compress, like a damp towel
take a warm sponge bath
dress in light, comfortable clothing
turn down the temperature in your room

Over-the-counter medications can help ease your fever and symptoms, like headaches and muscle pain:

ibuprofen (Advil, Motrin)
acetaminophen (Tylenol)
naproxen (Aleve, Naprosyn)

You may need treatment from your doctor for more serious causes of a fever. The treatment depends on the cause. Your doctor may prescribe medications to treat serious infections:

antibiotics
antivirals
antifungals

When to go the ER

A fever may be a sign of serious illness. A high fever can also cause serious side effects.

Emergency Symptoms
Get emergency medical attention by going to the ER or calling an ambulance if you have any of these symptoms:
seizure or convulsions
fainting or loss of consciousness
confusion
hallucinations
severe headache pain
stiff or painful neck
difficulty breathing
hives or a rash
swelling in any part of the body

The bottom line

A fever in adults is usually not harmful on its own. It is a sign that your body is dealing with an infection or other illness. In some cases a high or long-lasting fever can be a sign of a serious illness. You may need urgent medical treatment.

Do not ignore a fever. Get plenty of rest and fluids to help your body heal. See your doctor if you have a fever that lasts longer than 3 days or if you have other severe symptoms.

If you have a chronic condition or have been treated for a serious illness, let your doctor know if you have any kind of fever.

How we reviewed this article:

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Fever. (2018). https://www.cancerresearchuk.org/about-cancer/coping/physically/fever/what-is-fever
Fever in adults. (2018). https://www.health.harvard.edu/diseases-and-conditions/fever-in-adults2
Fever in adults. (2019). https://www.nhsinform.scot/illnesses-and-conditions/infections-and-poisoning/fever-in-adults
Mayo Clinic Staff. (2018). Fever.https://www.mayoclinic.org/diseases-conditions/fever/symptoms-causes/syc-20352759

Share this article

Medically reviewed by Alana Biggers, M.D., MPH — Written by Noreen Iftikhar, MD on September 17, 2019

Fever In Adults: Characteristics, Types, And When It's Serious

Health Conditions

Condition Spotlight

Wellness Topics

Product Reviews

Featured Programs

Featured

Lessons

Newsletters

Lifestyle Quizzes

Health News

This Just In

Top Reads

Video Series

Find Your Bezzy Community

Follow us on social media

What is a fever?

Types of fevers

When is a fever serious?

Causes of serious fevers

Treatments

When to go the ER

The bottom line

How we reviewed this article:

Read this next

Fever - Symptoms And Causes - Mayo Clinic

Fever (Children) | National University Hospital

How Long Does A Fever Last With A Virus?

How Long Does A Fever Last? - Coastal Urgent Care Houma

When To Worry About Fever In Adults - CareCentral Urgent Care

When To Take Your Child To The Doctor For A Fever – Cleveland Clinic

Fever In Adults | NHS Inform

Fever - SingHealth

Fever In Children - HealthHub

Fever In Adults - Infections - MSD Manual Consumer Version

What Is A Fever? Causes, Symptoms, And Treatment - Vicks

Fever (0-12 Months) - Seattle Children's

Fever - Seattle Children's

Fever - AboutKidsHealth

Contact