When Should You Go to the Hospital with a Fever?

Fevers are a natural response to infection and disease. They usually run their course when an infection dies off. But there are times when a fever climbs dangerously high for too long, causing permanent or life-threatening injury. Here’s how to know if your fever is signalling something serious — and when it’s time to go to the hospital.

What is a fever?

A fever is the body’s way of fighting disease and illness. It’s a temporary rise in body temperature that makes it harder for viruses and bacteria to survive. Fevers also trigger the immune system to work harder.

A fever is considered to be any sustained increase in temperature over the normal body temperature, which is a range that may differ from one person to the next. Normal body temperature can be as high as 37.5°C (by mouth) and can change about 0.5°C throughout the day. The average normal body temperature for an adult is 37°C (98.6°F). A low-grade fever can be as low as 37.3°C.

Your body temperature fluctuates throughout the day and during specific activities. It can rise in a hot room, during exercise, and even when you’re eating. Body temperature also rises during the second part of a woman’s menstrual cycle. These changes in temperature are normal and not considered a fever.

Though there are conditions like an infection that has spread throughout your body (known as sepsis), low blood sugar (hypoglycemia), or even an underactive thyroid that can cause low body temperatures, under 36.1°C. Hypothermia sets in at temperatures below 35°C.

Causes of a fever

The top causes of fevers include viral and bacterial infections, autoimmune diseases, and other common factors.

Viral and bacterial infections

Respiratory infections like colds, flus, ear and sinus infections, mononucleosis, and pneumonia
Urinary tract infections
Digestive tract infections, including viral and bacterial gastroenteritis
Bone infections
Meningitis
Organ infections such as appendicitis and cellulitis
Septicemia (can also cause low body temperatures)

Autoimmune diseases

Rheumatoid arthritis (RA)
Vasculitis (including periarteritis nodosa, a systemic vasculitis)
Crohn disease
Ulcerative colitis
Systemic lupus erythematosus (SLE)

Other causes

Hodgkin disease, non-Hodgkin lymphoma and leukemia
Certain medicines including some seizure medications and some antibiotics for example
Most vaccines including diphtheria, tetanus and acellular pertussis (DTaP), pneumococcal and COVID

Duration and severity of fevers

A fever typically lasts three to four days. A mild fever of 38°C or lower may not require medication, just supportive care like rest and hydration. Keep in mind, that temperature is not always an indicator of illness severity. Someone very sick may not have a very high fever, and someone with a very high fever may have a mild infection. A better gauge is how the person is looking and feeling— but remember, the fever is working to fight infection.

Identifying when to seek medical help

A fever is necessary to fight most infections, but that doesn’t mean you should let it ride without intervention, especially if it remains high or you also have other serious symptoms.

When is a fever considered too high?

In adults, a fever of 38°C is considered low grade, 38.1°C – 39°C is moderate, and 39.1° to 41°C is a high fever. A fever that stays at or keeps rising above 39.4°C or regularly rises to 40.5°C or higher is too high. Brain damage can occur at 42°C.

When should you go to hospital with a fever?

Seek medical attention if your fever does not resolve after three to four days, or if it is above 40°C. A low-grade or mid-grade fever that lasts or comes and goes for a week or longer — or a fever that doesn’t respond to medication — is also cause for concern. Other signs you should seek medical attention while experiencing a fever include:

Abdominal pain
Convulsions or seizures
Chest pain or difficulty breathing
Mental confusion, behavioural or speech changes
Painful urination
Rashes or new bruising
Severe headache
Stiff neck and pain when you bend your head forward
Unusual sensitivity to bright light
Vomiting and unable to keep up with hydration
Weakened immune system from other illnesses or therapy

Specific considerations for infants and children

Children show signs of illness quickly, but they also get better faster than adults in most cases. Depending on your child’s age signs their fever may require medical attention include:

A fever in a baby three months and under
A fever in a baby six months and younger should be seen by a healthcare provider
Babies three months and younger with a fever should be seen more urgently
Has a temperature > 40°C
Excessive irritability or fussiness
Is wheezing or having difficulty breathing
Repeated vomiting
A seizure
Seems confused or unable to move their limbs
Was left in a hot car
Has blue or purple lips or nails
Has a rash or any other worrisome sign to you

Call your healthcare provider if your child also experiences any of these symptoms:

Has other symptoms like an earache or sore throat
Recently had an immunization

Medical interventions for severe cases

If you or your child is experiencing any of the above signs, head to the hospital or clinic.

What to expect during a hospital visit

Knowing what to expect when you visit the hospital for a high fever can help reduce any fear and anxiety you might feel. Be prepared to tell your nurse practitioner or physician the following information to speed up the process:

Any and all symptoms
The duration of your fever and symptoms
The frequency and dose of many medications, including ibuprofen, acetaminophen and aspirin
Medical history
Recent travel history

Tests and examinations for fever diagnosis

The healthcare provider will perform a physical examination and order tests that may include blood work, nasal and throat swabs, and a urine sample, depending on the symptoms. If respiratory symptoms are present, they may also order a chest x-ray.

It can take some time to get the test results back, so be prepared to keep your child comfortable — bring their favourite blanket, toy, or book.

Treatment options available in a hospital setting

The first course of treatment for a high fever is often acetaminophen or a non-steroidal anti-inflammatory like ibuprofen or naproxen, which can also help relieve any related muscle pain. The hospital may administer IV fluids to fight dehydration or IV antibiotics if they find a bacterial infection.

Healthy habits to reduce the risk of fevers

The best way to prevent a fever is to adopt healthy habits that can help prevent infections:

Wash your hands often, especially after using the washroom and before eating.
Consider wearing a face mask and practice social distancing in crowded indoor locations
Don’t share cups, bottles, or utensils.
Carry hand sanitizer with you and apply it when hand washing is not available.
Avoid touching your mouth, nose, or eyes.
Consider vaccinations for common illnesses like influenza and COVID-19.

Home remedies for managing a fever

The most common side effects of a fever are dehydration and muscle aches. Water, herbal teas, and broths can help nourish you during a fever. Avoid giving young children sports drinks or juice for hydration.

Ibuprofen and acetaminophen can help reduce the fever and ease the discomfort of aches and pains. A lowered fever can also help bring about much-needed rest.

Take acetaminophen every four to six hours

Take ibuprofen every six to eight hours

Aspirin acetylsalicylic acid (ASA) is an effective fever reducer in adults but DO NOT give it to children as it can cause Reye’s syndrome, a very serious condition that can damage both the liver and brain.

Wear lightweight clothing and light blankets and keep your room comfortable — not too hot or cool. Resist the urge to pile on blankets when you have the chills since this can increase body temperature. Don’t use alcohol rubs or cold baths to bring the fever down — it can lead to chills and increase your body temperature.

It’s common for people with a fever to feel better after taking a fever reducer, but if you or a loved one is experiencing a prolonged fever or other serious symptoms, visit your healthcare provider or the nearest hospital.

The information presented here is for educational purposes and is not meant to replace the advice from your medical professional. Virtual care is not meant for medical emergencies. If you are experiencing an emergency like chest pain or difficulties breathing, for example, please call 911 or go to your nearest emergency room.