What Is It?
A fever is a higher-than-normal body temperature, usually meaning the body is responding to infection, inflammation, heat exposure, vaccination, or another trigger. In many adults and children, a temperature of around 38°C or above is generally considered a fever.
Fever itself is not usually a disease. It is a body response that shows the immune system or temperature-control system is reacting to something. Temperature readings can vary depending on whether they are taken from the mouth, ear, forehead, armpit, or rectum, so the person’s overall condition is also important.
Many short-term fevers are mild and improve within a few days, but fever should be taken more seriously if it is very high, persistent, worsening, or linked with worrying symptoms.
A fever is usually considered when body temperature is raised above normal and the person feels hot, shivery, sweaty, tired, or unwell. Other situations can look similar, including heat exhaustion, heatstroke, medication reactions, dehydration, inflammatory illness, or normal temperature changes after exercise or being in a hot environment.
Why Fever Is So Common
Fever is common because the body often raises temperature as part of its defence response. When the immune system detects an infection or inflammation, it releases chemical signals that tell the brain to increase body temperature.
People often search for fever because it can feel worrying, especially in babies, children, older adults, or people with chronic illness. Many want to know whether the fever is part of a simple viral infection, something heat-related, a reaction after vaccination, or a sign that medical attention is needed.
What Causes It?
Fever can have many causes. The most common are infections, but non-infective causes are also possible.
Common Causes and Triggers
Viral infections
Common colds, flu, COVID-19, viral sore throat, and viral stomach infections are frequent causes of fever. These may come with cough, sore throat, runny nose, body aches, diarrhoea, or tiredness.
Bacterial infections
Some infections, such as urinary tract infection, pneumonia, skin infection, ear infection, or bacterial throat infection, may cause fever and may need medical assessment.
Vaccination response
A mild fever can happen after some vaccinations as the immune system responds. This is usually short-term. However, severe, prolonged, or unusual symptoms after vaccination should be assessed.
Heat-related illness
High body temperature after heat exposure, heavy exercise, dehydration, or being in a hot enclosed space may suggest heat exhaustion or heatstroke rather than ordinary fever.
Medicines, inflammation, or other illness
Some medicines, inflammatory conditions, or other medical problems can cause raised temperature, especially if fever is persistent, unexplained, or keeps returning.
Fever is different from heatstroke. Fever is usually an internal body response to infection or inflammation. Heatstroke is a dangerous heat illness where the body overheats and may cause confusion, fainting, or very high body temperature.
What Should You Do?
If fever is mild and the person is otherwise well, first check the temperature, observe symptoms, encourage fluids, and allow rest. Avoid overheating the person with thick clothing or blankets.
What to Observe First
Pay attention to:
- Temperature reading and how it was measured
- How long the fever has lasted
- Whether the person can drink and pass urine normally
- Whether there is rash, breathing difficulty, severe headache, stiff neck, confusion, or persistent vomiting
- Whether there are symptoms such as cough, sore throat, diarrhoea, urinary pain, ear pain, or skin infection
- Whether fever started after vaccination, travel, heat exposure, or a new medicine
- Whether the person is a baby under 3 months old, child under 5 years old, pregnant, aged 65 years and above, or has chronic illness or weakened immunity
How Is It Usually Managed?
Fever is usually managed by monitoring the person’s overall condition, preventing dehydration, keeping them comfortable, and identifying possible causes. Fluids, rest, light clothing, and a comfortable room temperature are often helpful.
A pharmacist can help assess whether the fever sounds mild and self-limiting or whether medical review is safer. This is especially useful when fever occurs with cough, sore throat, diarrhoea, pain passing urine, rash, vaccination, travel, or regular medicines.
Ask a Pharmacist If Unsure
Ask a pharmacist if fever is mild but uncomfortable, if you are unsure how to measure temperature correctly, or if you need advice for a child, pregnant woman, older adult, or someone taking regular medicines.
Do not rely only on the number on the thermometer. How the person looks, behaves, drinks, breathes, and responds is also important.
When to See a Doctor
Seek medical advice urgently if fever is linked with:
- Baby under 3 months old with temperature 38°C or above
- Child aged 3 to 6 months with temperature 39°C or above
- Temperature around 40°C or above, especially if the person looks very unwell
- Fever lasting more than 3 days
- Fever with no clear cause that persists or keeps returning
- Breathing difficulty, chest pain, or blue lips
- Confusion, extreme drowsiness, fainting, seizure, or stiff neck
- Severe headache, persistent vomiting, or severe abdominal pain
- Rash that does not fade when pressed with a glass or finger
- Signs of dehydration, such as very little urine, dry mouth, sunken eyes, or unusual sleepiness
- Fever after overseas travel
- Fever in pregnancy, adults aged 65 years and above, or anyone with cancer treatment, organ transplant, HIV, diabetes, kidney disease, heart disease, or weakened immunity
Quick Summary
- A fever means body temperature is higher than normal, commonly around 38°C or above.
- It is often a body response to infection, inflammation, vaccination, heat exposure, or medicines.
- Temperature readings can vary, so the person’s overall condition matters.
- First observe temperature, duration, drinking, urination, breathing, rash, alertness, and other symptoms.
- Seek medical help for young babies, prolonged fever, very high temperature, severe symptoms, dehydration, pregnancy, older adults, or weakened immunity.
FAQ
What is a fever?
A fever is a higher-than-normal body temperature, commonly around 38°C or above, often caused by the body responding to infection or inflammation.
Is 38°C always dangerous?
No. A temperature around 38°C can happen with many short-term infections. The person’s age, symptoms, hydration, breathing, alertness, and duration matter.
Is fever serious?
Many fevers are mild and short-term, but fever can be serious in babies under 3 months old, pregnant women, adults aged 65 years and above, or people with severe symptoms or weakened immunity.
Is fever contagious?
Fever itself is not contagious. However, the infection causing the fever may spread to others, depending on the cause.
How long does fever usually last?
Many mild viral fevers improve within 2 to 3 days. Fever lasting more than 3 days, worsening, or linked with red flags should be checked.
Can fever go away on its own?
Yes. Some mild fevers settle as the body recovers. However, persistent, very high, or worrying fever should not be ignored.
Is fever the same as heatstroke?
No. Fever is usually an internal body response to infection or inflammation. Heatstroke is dangerous overheating from heat exposure and needs urgent medical help.
When should I see a doctor for fever?
See a doctor urgently for fever in a baby under 3 months old, fever lasting more than 3 days, temperature around 40°C or above, breathing difficulty, confusion, stiff neck, seizure, rash that does not fade when pressed, dehydration, pregnancy, older age, or weakened immunity.