Fever in Adults
Informed by recognized medical guidance
Overview
Fever is a temporary increase in body temperature, usually because your body is fighting an infection. A normal temperature is around 36–37°C (96.8–98.6°F). Fever is a sign that your immune system is working, not an illness itself.
Key facts
- Fever is a common response to infection and usually harmless.
- For adults, a temperature of 38°C (100.4°F) or higher is generally considered a fever.
- Most fevers go away on their own within a few days.
- How you feel matters more than the number on the thermometer.
Yes, fever in adults is very common. Almost everyone experiences a fever at some point due to infections like colds, flu, or other illnesses.
Fever can affect anyone, but adults with weakened immune systems, chronic health conditions, or who are very young or very old may have a harder time fighting off the underlying cause.
Symptoms
- Severe headache with stiff neck
- Difficulty breathing
- Rash that looks like small bruises or doesn't fade when pressed
- Seizures (fits)
- Loss of consciousness or confusion
- Extreme weakness or difficulty waking up
- ⚠Fever that lasts more than 3 days
- ⚠Fever that keeps going away and coming back
- ⚠Severe pain anywhere in the body
- ⚠Difficulty swallowing
- ⚠New confusion, especially in older adults
- ⚠Signs of dehydration (dark urine, very dry mouth, not urinating much)
Common symptoms
- Feeling hot or flushed
- Sweating or chills
- Headache
- Muscle aches
- Feeling weak or tired
- Loss of appetite
Symptoms in children
- Fever in children is common, and they may also be irritable, clingy, or have a poor appetite.
- Children can quickly become dehydrated, so watch for signs like fewer wet nappies or dry mouth.
Symptoms in older adults
- Older adults may have a lower baseline temperature, so a fever might not be as high; pay attention to changes in behaviour like confusion or increased falls.
- They are at higher risk of dehydration and complications from the cause of the fever.
Causes
Main causes
- Infections such as colds, flu, chest infections, urinary tract infections, or stomach bugs
- Inflammatory conditions like rheumatoid arthritis
- Heat exhaustion or heatstroke
- Reaction to certain medications (always check with your doctor)
- Rarely, more serious conditions like an infection inside the body or cancer
Risk factors
- Having a weakened immune system (e.g., due to chemotherapy, HIV, or long-term steroid use)
- Recent surgery or hospital stay
- Travel to areas with different infectious diseases
- Chronic conditions like diabetes, heart disease, or lung disease
- Age over 65
When to see a doctor
See a doctor urgently if:
- Fever over 40°C (104°F) that doesn't come down with rest and fluids
- Fever with a severe headache, stiff neck, or rash
- Fever after returning from a country with tropical diseases
- If you have a serious medical condition and develop a fever
Book a routine appointment if:
- Fever lasting more than 3 days without improvement
- Mild fever that concerns you – a quick check with your GP can give peace of mind
Diagnosis
Your doctor will ask about your symptoms, check your temperature, and examine you. They may listen to your chest, check your throat, and feel your abdomen. This helps find the cause of the fever.
Tests that may be done
- Urine test to check for infection
- Blood tests to look for signs of infection or inflammation
- Chest X-ray if a lung infection is suspected
- Sometimes a throat swab or other samples depending on symptoms
What to expect at your appointment
Most fevers are diagnosed and managed without special tests. Your doctor will explain what they think is causing your fever and whether you need any treatment. If a serious infection is suspected, you may be referred to a hospital for more tests.
Treatment
Treatment focuses on making you comfortable and treating the underlying cause. Most fevers do not need medicine – they will go away on their own.
Self-care at home
- Rest – your body needs energy to fight the infection.
- Drink plenty of fluids like water or clear soup to stay hydrated.
- Wear lightweight clothing and keep the room at a comfortable temperature.
- Use a cool, damp cloth on your forehead if you feel overheated.
- Avoid alcohol and caffeine, which can dehydrate you.
Medical treatments
If the cause of the fever is a bacterial infection, your doctor may prescribe antibiotics. For viral infections, antibiotics do not work. There are over-the-counter medicines that can help lower fever and ease aches – always follow the package directions and talk to your pharmacist or doctor about what is right for you. Do not take aspirin for fever unless advised by a doctor, as it can cause side effects in some people.
When is surgery considered?
Not applicable
Living with this condition
While you have a fever, take it easy. Stay home from work, rest, and drink fluids. Monitor your temperature and symptoms. Most people feel better within a few days.
Lifestyle tips
- Get plenty of sleep to support your immune system.
- Wash your hands often to avoid spreading germs to others.
- Cover your mouth when you cough or sneeze.
Diet and exercise
Eat light, easy-to-digest foods if you have an appetite – like soup, toast, or bananas. Avoid heavy, greasy foods. Do not exercise while you have a fever; wait until your temperature is normal and you feel strong again.
Mental health and emotional wellbeing
Having a fever can make you feel tired, irritable, or down. This is normal and usually passes as you recover. If you feel very anxious or depressed about your health, talk to your GP.
Prevention
You cannot prevent all fevers because they are a natural response to infection. But you can reduce your risk of infections that cause fever.
Vaccines
Vaccines such as the flu vaccine (influenza) and other routine vaccinations can prevent some infections that cause fever. Talk to your doctor about which vaccines are right for you.
Screening programmes
No routine screening exists for fever itself. Regular health checks can help manage conditions that make you more prone to infections.
Complications
If left untreated
- Dehydration from not drinking enough fluids
- Febrile seizures (more common in children but can occur in adults with very high fever)
- Delirium or confusion, especially in older adults
- Rarely, organ damage if the cause of the fever is a severe infection like sepsis
Long-term outlook
For most people, fever is a short-lived response that passes without any problems. With rest and fluids, you will likely feel better in a few days. If the fever is due to a more serious infection, early treatment gives a good chance of full recovery.
Find support
International organisations
Local organisations
- NHS – Fever in adults ↗ · United Kingdom
Helplines
External links open third-party websites. Ruqelo Health is not responsible for external content. Listing an organisation does not imply endorsement.
Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
Related conditions
Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 16, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.
Guidance may differ by country or region. Confirm local recommendations with a qualified healthcare provider.