What is a fever?
A fever is a temporary rise in body temperature that commonly occurs when the body is responding to an illness. In adults, a temperature of around 38°C (100.4°F) or higher is commonly considered a fever, although normal temperature varies between people and changes during the day.
How the temperature is measured also matters. If you are monitoring a fever, note the temperature, the time it was measured and the method used. This information can be useful when discussing your symptoms with a healthcare professional.
Common causes of fever
Infections are a common reason for fever. Respiratory infections, gastrointestinal infections, urinary infections and other infections can all cause an elevated temperature.
Fever can also occur with inflammatory or other medical conditions, and some medicines or other factors can affect body temperature. The cause cannot always be determined from the temperature alone.
Symptoms that can occur with fever
Depending on the underlying cause, fever may occur with symptoms such as:
- Chills or feeling unusually cold
- Sweating
- Headache
- Body aches or tiredness
- Cough, sore throat or runny nose
- Nausea, vomiting or diarrhea
- Urinary symptoms
- Other symptoms related to the underlying illness
The combination of symptoms, their duration and your medical history are often more useful than the temperature alone when deciding what to do next.
What can you do at home?
If you are otherwise well and the illness appears mild, supportive care can often be started at home while you monitor your symptoms.
Rest and stay hydrated
Rest and drink enough fluids to reduce the risk of dehydration. Water is a simple choice. If you are losing fluids through vomiting or diarrhea, you may need appropriate oral rehydration support.
Monitor your symptoms
If you have a thermometer, record your temperature and notice whether your symptoms are improving, staying the same or getting worse. Also pay attention to your ability to drink fluids, pass urine and carry out normal activities.
Fever-reducing medicines
Medicines such as paracetamol or ibuprofen may be used by some adults when they are uncomfortable, but they are not appropriate for everyone. Your other medicines, medical conditions, allergies, pregnancy status and the possible cause of the fever can affect what is suitable.
Follow the product instructions or advice from a qualified healthcare professional. Avoid taking multiple products containing the same medicine ingredient.
When should you see a doctor?
Consider medical evaluation when a fever is persistent, worsening, repeatedly returning, unusually high, or accompanied by symptoms that are concerning.
Medical assessment is particularly important if you have a weakened immune system, significant chronic illness, are taking medicines that suppress immunity, or have recently travelled and developed a fever.
A healthcare professional may need to examine you and decide whether tests such as blood tests, urine testing or imaging are appropriate. The investigation depends on the symptoms and suspected cause.
Warning signs that need urgent medical attention
Seek urgent in-person medical care if fever occurs with symptoms such as:
- Difficulty breathing or significant shortness of breath
- Chest pain or persistent chest pressure
- Confusion, unusual behavior or difficulty staying awake
- Seizure
- Severe weakness or inability to walk normally
- Severe or rapidly worsening headache, especially with a stiff neck
- Repeated vomiting with inability to keep fluids down
- Very little or no urine, especially with signs of dehydration
- A concerning new rash or bleeding/bruising
- Severe or rapidly worsening abdominal pain
What about children, pregnancy or other special situations?
This article is specifically about fever in adults. Fever in infants and children requires different considerations, and pregnancy, older age, immunosuppression and significant chronic illness can also change how fever should be assessed.
If you are pregnant, caring for a young child, immunocompromised, or have a significant chronic medical condition, seek appropriate medical advice rather than relying only on general information in this article.
Can fever be assessed through an online consultation?
Some non-emergency fever presentations may be suitable for an initial online medical consultation, depending on the symptoms, duration, medical history and other clinical information.
An online consultation cannot replace physical examination, vital-sign assessment, laboratory testing or imaging when these are clinically needed. The doctor should determine whether remote consultation is appropriate and whether you need in-person evaluation.
Need medical guidance?
For an appropriate non-emergency concern, you can learn more about consultation with Dr. Bhagirath Vagh, MBBS.
Consult Dr. VaghFrequently asked questions
What temperature is considered a fever in adults?
A temperature of about 38°C (100.4°F) or higher is commonly considered a fever in adults, although temperature varies with the person, time of day and measurement method.
Is every fever caused by an infection?
No. Infections are a common cause, but fever can also occur with inflammatory conditions, some medicines and other medical problems.
Should I take antibiotics for fever?
Not automatically. Antibiotics treat certain bacterial infections, not viral illnesses. The need for an antibiotic depends on the suspected cause and clinical assessment.
When is fever an emergency?
Fever accompanied by symptoms such as difficulty breathing, severe chest pain, confusion, seizure, inability to stay awake or severe dehydration symptoms requires urgent medical attention.