types of fever

Fevers are a difficult medical condition that none of us want to be in. However, it is unavoidable and all of us are affected by fevers from time to time. Also known as pyrexia or controlled hyperthermia, it is often a potential sign that not all is well with our body, and it is facing something unusual. Fevers are caused due to many reasons, including overexposure of skin to sunlight, infections, etc., but we shall discuss it in detail in a dedicated section. Apart from that, today, in this article, we shall be talking about everything you should know about pyrexia, types of fever, etc. However, before that, let us understand what we actually mean when we say someone is suffering from fever.

What Is A Fever?

Ideally, when everything is well within our body, the normal body temperature ranges between 36.1° C to 37.2° Celsius. However, if for some reason, the body temperature increases beyond that, it might be due to a condition called fever.

Centers for Disease Control and Prevention considers a temperature of over 100.4 degrees Fahrenheit as a fever. It is usually a normal reaction of our body to several conditions including infections. In other words, it is a side-effect of ailments like cold, influenza, infections, etc., and it indicates that our immune system is effectively fighting the infection or illness.

Whenever our body is infected from any flu or any antigens, our immune system produces more white blood cells, which stimulate the brain to heat up the body. This, in turn, results in fever. Then, our body reacts to this and tries to cool down itself by contracting muscles and limiting the blood flow to the skin. This causes body and muscle aches, and chills.

Usually, it is not a cause of concern and you do not need to see a doctor unless the temperature reaches a temperature of 103 degrees Fahrenheit. If the temperature is below that, the fever goes off by itself in a few days once the antigens in the body are defeated by your immune system. However, if the fever continues to persist and does not doze off by itself, you need to meet your doctor at the earliest.

How Do I Get To Know If I Have Fever?

The most common way to know that a person has a fever is by the discomfort he feels and increased body temperature. However, some of the most common symptoms of fever include sweating, chills, fatigue, weakness, headache, muscle ache, poor appetite, dizziness, etc.

Apart from that, you might also get vomiting sensation, dehydration, muscle cramps, abdominal pain, skin rashes and sensitivity to light, etc. If you have fever with these symptoms and the temperature is above 103 °F or 39 °C for more than three days, we suggest you immediately seek medical help, as it could lead to severe circumstances, if not treated on time.

What Are The Most Common Causes Of Fever?

Usually, you get fever when your body is invaded by an antigen, including bacteria, fungi, drugs, viruses, and other similar toxins. Apart from that, a person suffers from fever when he gets infected with issues like cold, gastroenteritis, flu, etc.

Children might also get fevers if they are given vaccine shots, and adults can get it due to other health conditions like asthma, rheumatoid arthritis, liver diseases, diabetes, etc. Other reasons include bacterial infection, inflammation, food poisoning, heat exhaustion, sunburn, etc.

What Are The Different Types Of Fever?

Fevers can be classified based on two different factors, including the temperature and the duration of fever. Let us now discuss the different types of fever based on these factors.

Based On the Temperature

Based on the temperature of fever, it can be classified as low-grade fever, moderate fever, high-grade fever, or hyperpyrexia.

1. Low-Grade Fever

As mentioned previously, the normal temperature of the body ranges between 36.1° C to 37.2° Celsius. However, if the temperature increases to 38° C (100.4 F), it can be considered as a low-grade fever. A low-grade fever is also known as ‘mild fever’, and is usually not a reason to worry. A mild fever typically goes off by itself in a couple of days, upon intake of a proper diet.

2. Moderate Fever

If the temperature of the body ranges between 39.1 and 40° C (102.2 to 10.4F), it can be termed as a moderate fever. This might require you to have a stricter control on your diet to get rid of this fever.

3. High-Grade Fever

If the temperature of the body goes beyond 39.4° C (104F), it can be considered as a high-grade fever. It can be a serious condition, and requires immediate medical attention. You might need to take relevant medication and be under observation in some cases to get rid of high-grade fever.

4. Hyperpyrexia

Hyperpyrexia is when the temperature of the body increases beyond 41.1° C (106F). This is a rare occurrence and needs immediate medical attention. In this case, you might also need to skip on certain foods, and have controlled medication.

Based On the Duration of Fever

Based on the duration of fever, it can be classified into either acute, sub-acute, or chronic fever.

1. Acute Fever

Acute fever is when the duration of the fever is less than seven days. It is usually a mild fever and is the most common fever-type among people.

2. Sub-Acute Fever

If a fever lasts for up to 14 days, it is termed as sub-acute fever. It has fewer instances of occurrence when compared to acute fever. It might require medical and blood tests to be done to identify the cause of fever, so that proper medication can be suggested.

3. Chronic Fever

If a fever continues to persist for over 14 days, it is known as chronic or persistent fever. While the occurrence of this type of fever is uncommon, it is a strong indication of poor health or severe infection, and could be serious even if it is a mild fever. Hence, immediate medical attention is needed, and could require medical and blood tests to identify the root cause of such persistent fever.


Fever is a state when the temperature of the body increases beyond the normal range, and causes discomfort, including sweating, chills, fatigue, weakness, headache, muscle ache, poor appetite, dizziness, etc.

Based on the temperature range, the types of fever can be classified as mild, moderate, high-grade fever, or hyperpyrexia, which is the maximum fever one can get. On the other hand, a fever can be acute, sub-acute, or chronic based on the duration of fever.

A fever can be caused due to various reasons, including viral infections (like a flu or cold), fungal infections, bacterial infections, etc. Apart from that, if you are suffering from Asthma, diabetes, arthritis, etc., you might see risen temperatures often.

A mild fever usually lasts for a few days and goes off by itself. However, if it lasts for a longer time, we suggest you to immediately consult your doctor and get proper medication. However, please note that you should never take any medication without consulting your doctor.

It is common for people to suffer from fevers, and is not a reason to worry, as it indicates that your immune system is healthy and fighting the antigens attacking your body. Once the immune system kills the antigens, the temperatures should lower automatically and fever goes off. However, if fever continues to persist for longer periods despite taking medication, you must get your blood tests done to find the root cause of the same, and get it treated.


1. Why does fever increase at night?

The intensity of fever increases at night because during this time, the inflammatory response of your immune system amplifies exponentially. It kills the virus attacking you more effectively during this time, and even the production of hormones like cortisol and adrenaline is suppressed when we sleep.

2. How many days of fever is normal?

The duration of fever varies in different people and depends upon the intensity of fever. However, it usually lasts for three or four days, and goes off upon taking medication. If it lasts for a longer period, we suggest you seek immediate medical attention to get it cured.

3. What is the fastest way to cure viral fever?

The fastest and the best way to cure a viral fever is by taking medication at the right time when you feel discomfort due to fever. However, we suggest consulting your doctor before you take any tablet or medicine, as taking wrong medication can have a negative impact and make the matters worse.

4. What is the highest fever ever?

Fevers that record a temperature of over 41.1° C (106F) are termed as hyperpyrexia, and require immediate medical attention. If not treated timely, such high temperatures can have a severe impact on your brain as well. However, it is a rare occurrence not commonly observed among people.

5. Which drug reduces fever?

If you are suffering from fever, you can choose between two types of over-the-counter (OTC) fever reducing medicines, including acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs). However, we suggest you consult your doctor before taking any medication, as taking a wrong medication can have a severe impact on your health and make matters worse.

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