Understanding Fever: Causes, Symptoms, and Treatment

A telltale heaviness behind the eyes, an unusual warmth across the forehead, and before long, you realise your body is not quite itself. Fevers have a way of interrupting everyday life and leaving you with both discomfort and uncertainty.

But most of the time, a fever is not something to fear. It is simply your body's way of protecting you from illness, whether caused by viruses (like the flu or COVID-19), bacteria (like those that cause tonsillitis or UTIs), or other pathogens. When you know what fever symptoms mean and how to manage them, you can tell when to rest it out and when to call a doctor.

What Actually Is a Fever?

Your body temperature isn't a fixed number. It shifts throughout the day: lower in the morning, slightly higher in the afternoon. The widely accepted average sits at 37°C (98.6°F), but anywhere between 36.1°C and 37.2°C is considered normal.

A fever is generally defined as a body temperature of 38°C (100.4°F) or above. At that point, a foreign invader, like a virus, bacterium, or other pathogen, has prompted your hypothalamus (a small region of the brain responsible for regulating body temperature) to reset its threshold.

What Causes a Fever?

A fever is not a disease, but a symptom. Here are the most common causes: 

Infections

Most of the time, the cause of fever is any active infection inside your body, such as: 

• Viral diseases such as the common cold, COVID-19, and the flu.
• Bacterial infections like urinary tract infections, tonsillitis, and pneumonia.
• Diseases spread by mosquitoes, such as malaria.
• Vomiting and diarrhoea due to gastrointestinal infections.

Non-Infectious Causes

Not every fever comes from a bug. Other triggers include:

• Inflammatory diseases such as rheumatoid arthritis.
• Some drugs or vaccines.
• Heat exhaustion
• Autoimmune disorders
• Cancer (lymphoma) and clots in the blood.

What Are the Common Symptoms of a Fever?

Fever symptoms can vary based on the cause and severity, but the most frequent ones to be considered are:

• A temperature of 38 °C or higher.
• Shivering (your body trying to produce more heat) and chills.
• Sweating
• Headache and aching muscles.
• Weakness and fatigue.
• Loss of appetite

• Dehydration ( if you are sweating a lot or vomiting)
• Skin flushing (increase in body temperature and the enlargement of blood vessels close to the skin, making the skin red or flushed)
• Dry cough
• Rapid heart rate (tachycardia)
• Eye pain/soreness

Higher fevers above 39.4°C (103°F) may also cause confusion, extreme irritability, hallucinations, or, in young children, febrile seizures. 

How Fever Presents Differently Across Age Groups

This is where most people get confused. A temperature of 102°F means something very different in a two-month-old than it does in a healthy adult. Here is a simple breakdown:

Older adults are particularly important to watch carefully. Their immune systems do not always produce a strong fever even when the infection is serious, which means a relatively low temperature can still indicate something that needs medical attention.

How is Fever Treated?

Most fevers can be managed at home. Here is what usually helps: 

At Home

Home treatment should be sufficient when your fever is less than 39.4 °C and is not bothering you:

• Keep yourself hydrated. Consume a lot of water, broths or oral rehydration fluids to replace the lost fluids through sweating.
• Watch out for symptoms of dehydration, including dark urine, dry mouth, or dizziness.
• Rest adequately. Your body needs energy to protect against infections, so do not engage in strenuous activities and get some additional sleep.
• Wear loose clothes. Although it is nice to be wrapped up, it will keep the heat trapped in your body, which will only aggravate the situation.
• Take paracetamol in case of any discomfort with your fever. Nevertheless, aspirin should not be administered to children below the age of 16 years since it can cause serious side effects.

When Should You See a Doctor For Fever?

Please do not wait it out longer than you need to. See a doctor if:

• Your temperature is 39.4°C (103°F) or higher.
• The fever persists for more than three days without improvement.
• You notice signs of dehydration (very dark urine, dry mouth, dizziness, or significantly reduced urination).
• You’ve got a stiff neck, intense headaches, or a skin rash along with the fever.
• You’re feeling super disoriented or can barely keep your eyes open.
• You’re having difficulty breathing or shortness of breath (may signal pneumonia or a severe respiratory infection).
• You have chest pain or persistent chest tightness.
• You’re experiencing persistent vomiting.
• A seizure (lasting more than five minutes) occurs.

Can You Prevent a Fever?

Fever is the natural defence of your body and therefore, you cannot prevent it all the time. But preventive measures can help in eliminating the possibility of contracting diseases that cause a fever, and they include:

• Washing hands regularly, particularly before eating and after visiting the bathroom.
• Keeping vaccinations current and having annual flu shots.
• Stay away from individuals who are showing signs of sickness.
• Keep your immune system in good health with sufficient sleep, a good diet and proper stress management.
• Stay hydrated and drink at least 8 - 10 glasses of water per day.
• Protect yourself from mosquito bites to stay away from dengue fever or malaria. Wear light and loose clothes, long-sleeved shirts and full-length pants whenever you go outside. 

Get Expert Care for Your Fever at Apollo Clinic!

A fever can feel overwhelming, particularly when you have no idea what is causing it or how serious it is. But you don't have to deal with it alone.

At Apollo Clinic, you can consult experienced general physicians who’ll actually address your fever symptoms and pinpoint what’s going on with on-site diagnostics. Book a consultation with an Apollo Clinic doctor for timely diagnosis and personalised care.

FAQs

• Can a fever come back after it seems to have gone away?

Yes, it is referred to as a relapsing or a biphasic fever, and it may occur with some infections, such as some viral diseases and dengue fever.

• Why do I shiver when I have a fever if my body temperature is already high?

Shivering happens because your brain's thermostat has been reset to a higher temperature, and your body is working hard to reach that new target.

• Can stress actually cause a fever?

Yes, sometimes that happens. There’s even something called psychogenic fever, basically when your body temperature goes up because of emotional stress rather than infection.

• How do I know if I'm properly hydrated while recovering from a fever?

A simple check: the colour of your urine. Pale yellow means you're well hydrated; dark yellow or amber suggests dehydration and a need to increase your fluid intake.