Fever range: Fever is one of the clearest signs that your body is fighting an infection. You may feel tired, shivery or just “not yourself,” and the first instinct is often to check your temperature, but how much is really a cause for concern?
What is a fever?
A fever means your body has turned up its internal thermostat to help fight an infection. It’s part of your natural defence system, making it harder for germs like bacteria and viruses to survive. A normal body temperature is around 98.6°F, although it can fluctuate slightly throughout the day depending on activity, time and even hormones. In general, a temperature of 100.4°F (38°C) or more is considered a fever.
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Different levels of fever
Low-grade fever:
- Temperature: 99.5°F–100.3°F (37.5°C–37.9°C)
- How it feels: You may feel slightly warm, slightly tired or sweaty, but you can usually go about your day and do most normal activities.
Moderate fever:
- Temperature: 100.4°F–102.2°F (38°C–39°C)
- How it feels: The discomfort increases. Chills, body aches, headache and weakness are common, and you’ll likely want to rest more.
High fever:
- Temperature: 102.3°F–104°F (39.1°C–40°C)
- How it feels: You feel quite sick. Shivering, intense tiredness, and sometimes confusion can appear. Children may be extra irritable, clingy or cry more than usual.
Very high or dangerous fever
- Temperature: 104°F (40°C) or higher
- How it feels: This is the danger zone. There may be confusion, hallucinations, a speedy heartbeat, or even seizures, especially in kids, older adults or people with other health problems. This level of fever needs urgent medical attention.
When is a fever serious?
Not every fever is an emergency. Often, it’s just your body doing its job. However, some warning signs mean you shouldn’t wait it out at home. Call a doctor or seek medical help quickly if you notice:
- A temperature above 103°F (39.4°C) that doesn’t come down with fluids and basic medicines
- Fever that lasts more than 3 days
- Severe headache or a stiff neck
- Difficulty breathing, fast breathing or chest pain
- A rash that spreads quickly or looks unusual
- Vomiting or diarrhoea that keeps coming back and risks dehydration
- Extreme tiredness, confusion, irritability or strange behaviour
These signs may indicate a more serious condition and should be checked by a doctor as soon as possible.
What causes a fever?
A fever is a symptom, not a disease. Many things can raise your temperature, and some are relatively harmless. Common causes include:
- Infections: Colds, flu, COVID-19, ear infections, throat infections, urinary tract infections and many others
- Vaccinations: It’s quite common, especially in children, to get a mild fever for a short time after certain shots
- Heat exhaustion or heatstroke: From spending too long in very hot weather or doing intense activity in the heat
- Inflammatory conditions – such as some forms of arthritis or autoimmune diseases
- Side effects of medicines – a few drugs can rarely cause fever as a reaction
- Teething in babies may cause a slight rise in temperature, but usually not a true high fever
How to manage a fever at home?
When you have a fever, your body is already doing the hard work of fighting an infection. Your job is to support it:
- Stay hydrated. Fever and sweating make you lose fluids quickly.
- Dress lightly and keep the room cool.
- Skip ice-cold baths or ice packs on the skin.
- Rest properly.
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Remember, a fever is usually a sign that your body is fighting back, not “failing.” Most mild to moderate fevers resolve on their own within a couple of days with rest and fluids. However, if the temperature is very high and continues to rise, consult a doctor and do not try to “wait it out” at home.