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π©Ί Medically reviewed by the Health Decoded Guide Editorial Team · Last reviewed: July 2026
π Quick Summary
Fever is a temporary rise in body temperature, usually caused by the body's immune response to an infection or inflammation.
Most fevers improve on their own, but some may be a sign of a more serious illness that requires medical attention.
1οΈβ£ Introduction
Fever is one of the body’s most misunderstood signals and is one of the body's most common responses to illness.
It is not a disease itself, but a sign that the immune system is reacting to an infection, inflammation, or another underlying condition.
π In many cases, fever is part of the body's natural defense against illness rather than the illness itself.
2οΈβ£ How it happens
Fever occurs when the brain resets the body’s temperature.
• the hypothalamus raises the temperature set point
• immune system releases signals during infection
• the body reduces heat loss and increases heat production until it reaches the new temperature set point.
π The higher temperature may help slow the growth of some bacteria and viruses while supporting the immune response.
3οΈβ£How high is a fever?
• Low-grade fever: usually below 39°C
• High fever: 39°C or higher
π The temperature is important, but how long the fever lasts and how the person feels are often even more important.
4οΈβ£ Common causes
πΉ Infectious causes
→ Viral infections
→ Bacterial infections
πΉ Other causes
- Malaria
- Typhoid (region-dependent)
- Autoimmune conditions
- Inflammatory Conditions
5οΈβ£ What a fever may feel like
• feeling hot
• sweating
• chills or sweating
• body aches and fatigue
π These occur due to immune activation and temperature regulation.
6οΈβ£ Associated symptoms
• headache
• weakness
• nausea/loss of appetite
• dehydration
• cough
• sore throat
π Associated symptoms help identify the underlying cause.
7οΈβ£π©Ί When it becomes dangerous π¨
• fever above 39°C
• fever lasting more than 3 days
• confusion
• seizures
• difficulty breathing
• stiff neck
• persistent vomiting
• severe abdominal pain
π These may indicate:
• serious infection
• need for urgent medical evaluation
8οΈβ£ Management / treatment
• drink plenty of fluids to reduce the risk of dehydration.
• rest and avoid overheating
• use fever-reducing medication if needed
9οΈβ£ Diagnosis
• clinical assessment
• history of symptoms and exposure
• tests if cause unclear
π The focus is identifying the underlying cause.
π’ Important message
Fever is often a sign that your body is responding to an illness.
π The most important thing is not just the temperature, but how you feel overall and whether any warning signs are present.
FAQ
What temperature counts as a fever?
A body temperature of 38°C (100.4°F) or higher is generally considered a fever.
Should I always lower a fever?
Not always. Fever is part of the body's natural defence. Treatment is mainly recommended for comfort or if the fever is high or causing significant symptoms.
When should I worry about a fever?
Seek medical care if your fever is very high, lasts more than three days, or is accompanied by warning signs such as confusion, difficulty breathing, severe headache, seizures, or a stiff neck.
Can fever cause dehydration?
Yes. Fever increases fluid loss through sweating, so drinking plenty of fluids is important to help prevent dehydration.
Is every fever caused by an infection?
No. Although infections are the most common cause, fever can also occur with inflammatory conditions, autoimmune diseases, certain medications, and other medical conditions.
π Related Health Topics
• Headache
• Typhoid Fever
• Common cold
• Weakness
• Malaria
• Diarrhea
• Gastroenteritis
π Medical References
• National Health Service (NHS). Fever in adults.
• National Health Service (NHS). Fever in children.
• Mayo Clinic. Fever.
• MSD Manual Consumer Version. Fever in Adults.
• American Academy of Pediatrics (AAP). Fever.
β οΈ Medical Disclaimer
This article is for educational purposes only and does not replace professional medical advice.
If you have symptoms or concerns, please consult a qualified healthcare professional.