Dr. Nadheer K M (AIIMS)MBBS

July 11, 2017

March 06, 2020


Human body temperature is maintained at 37°C or 98.6°F. Fever is a term used to describe an increase in the body temperature by about 1°C. Fever is believed to be the body’s defence mechanism to fight disease-causing pathogens.

There are countless causes of fever. It ranges from simple to complex depending on the causative agent, duration, and type of fever. The metabolic processes in the body are critically temperature dependent and a person’s body temperature rarely varies by more than 1°C from baseline. 

Over the counter medicines like paracetamol are effective in reducing mild fever. But if tests reveal an infection then appropriate treatment is needed as per your doctor’s advice.

What is a fever

Fever is defined as a temporary elevation of the body temperature, usually due to an underlying illness. Medically, fever is termed as pyrexia or febrile response and is defined as having a temperature above the normal range due to the entry of a pathogen (a bacterium, virus, or other microorganisms that can cause disease) or foreign particle.

It is caused due to numerous reasons but infections are the most common cause. Fever is generally a sign that there is some disturbance in the body caused by a pathogen and that the body is trying to fight it off on its own. Fever usually doesn’t last for more than a few days (2-5 days maximum) depending upon the causative agent and your body’s immunity. There are over the counter drugs available to bring the temperature down but if the fever is mild, it is better to leave it untreated if it is within the normal range.

myUpchar doctors after many years of research have created myUpchar Ayurveda Urjas Capsule by using 100% original and pure herbs of Ayurveda. This ayurvedic medicine has been recommended by our doctors to lakhs of people for sex problems with good results.
Long Time Capsule
₹719  ₹799  10% OFF

Types of fever

Fever is classified based on the symptoms or bouts in a defined time period or as per a well -defined pattern. It is classified as:

  • Continuous fever
    The body temperature remains above normal throughout a 24-hour period but does not fluctuate by more than 1°C. It occurs in typhoid, UTI (urinary tract infections) and typhus.
  • Remittent fever
    The body temperature remains above normal throughout a 24-hour period but does not fluctuate by more than 2°C. This type of fever is associated with typhoid and infective endocarditis.
  • Hectic or Septic fever
    The temperature variation between the peak and the normal value is very wide and exceeds 5°C. This is seen in conditions such as septicemia (the presence of infection in the blood).
  • Pal-Ebstein fever
    There are alternate fever and non-fever periods during the day. The temperature may take 3 days to rise, remain high for 3 days, and then remit in 3 days, followed by more fever for 9 days. This type of fever occurs in Hodgkin’s Lymphoma.
  • Low-grade fever
    Fever is present for several days but does not exceed 37.8°C at any time. Usually, it does not indicate any particular disease, but it is associated commonly with tuberculosis.
  • Step-ladder fever
    Temperature rises gradually to a higher level with each spike, so that a new plateau is higher than the preceding one, just like steps of a ladder. Examples include typhoid fever.
  • Relapsing fever
    Febrile episodes (fever) are separated by intervals of normal temperature. The fever when occurs may last from 2-9 days and then temperature gets normal. But, it may relapse after a period of few days repeating the same cycle. Such a pattern is seen in Borrelia infections.
  • Inverse fever
    The temperature rises early in the morning rather than in the evening such as in miliary tuberculosis.
  • Night Sweats
    A rise in body temperature is evident in the evening hours or the person may wake up at night due to sweating. Night sweats are common in tuberculosis, leukaemias, autoimmune disorders, and AIDS.
  • Intermittent fever
    The temperature rises for only some hours in a day and remains normal throughout the remaining hours. Examples include Malaria, kala-azar, septicaemia. It has the following subtypes:-
    • Quotidian: Spike in temperature occurs daily.
    • Double quotidian: The body temperature rises twice in a day, mostly during morning and evening such as in miliary tuberculosis.
    • Tertian: A rise in body temperature occurs every alternate day such as in malaria.
    • Quartan: The temperature rise occurs every third day such as in Malaria.

Fever can also be classified as acute, sub-acute, and chronic based on the duration of fever. Acute fever (2 weeks duration) is a characteristic feature of viral infections and upper respiratory tract infection. Sub-acute type of fever (usually not more than 2 weeks in duration) is seen in people with typhoid and intra-abdominal abscess. Chronic or persistent fever (>2 weeks duration) is typical of chronic bacterial infections such as tuberculosis, viral infections like HIV, cancers, and connective tissue diseases. However, any cause of acute fever can become persistent or chronic if untreated.

Stages of fever

Stages of fever are classified as follows:

  Celsius Fahrenheit
Hypothermia <35°C <95°F
Subnormal 35-36.7°C 95-97°F
Normal 36.7-37.2° C 98-99°F
Mild Fever 37.2-37.8°C 99-100°F
Moderate Fever 37.8-39.4° C 100-103°F
High Fever 39.4-40.5°C 103-105°F
Hyperpyrexia >40.5°C >105°F

Fever symptoms

Of all the manifestations of infection in humans, fever is the most common and most constant one. Fever can be accompanied by the following symptoms:

myUpchar doctors after many years of research have created myUpchar Ayurveda Kesh Art Hair Oil by using 100% original and pure herbs of Ayurveda. This Ayurvedic medicine has been recommended by our doctors to more than 1 lakh people for multiple hair problems (hair fall, gray hair, and dandruff) with good results.
Bhringraj Hair Oil
₹599  ₹850  29% OFF

Causes of fever

Infections or entry of a foreign particle is usually the cause of the fever. Fever is the body’s defence mechanism to fight off the effects of the foreign particle. The possible causes of fever are as follows:

  • Viruses
    They cause upper respiratory tract infections like a sore throat, nasal discharge, sneezing, and sinus pain.
  • Bacteria
    Diseases like Cholera, Gastroenteritis, Tonsillitis, Pneumonia, Urinary tract infections, etc. are all caused due to bacterial entry in the body.
  • Chronic illnesses
    Chronic diseases like ulcerative colitis cause fever which lasts longer than 2-3 weeks.
  • Tropical diseases
    Diseases like malaria and typhoid cause recurring fever.
  • Drugs
    Drug fever is caused sometimes in patients who consume penicillin and cephalosporins, sulphonamides, anticonvulsants etc.
  • Cancer
    Malignant (cancerous) tumours affecting any body part. may also cause fever.
  • Alcohol consumption
    Consuming alcohol above normal tolerable limit leads to liver cirrhosis (liver damage and irreversible scarring of the liver) causing fever.
  • Skin disorders
    Skin diseases like a rash may also lead to a rise in body temperature.
  • Heat exhaustion.
  • Inflammatory conditions like rheumatoid arthritis
    Rheumatoid arthritis, which is a condition where the person has inflammation of the joints may also lead to the development of a fever.
  • Immunizations and vaccinations
    Vaccinations like DTaP vaccine, pneumococcal vaccine, tuberculosis vaccine, etc. also cause fever in children.
  • Unknown cause
    Sometimes, a specific cause of fever isn’t known. This is termed as PUO (Pyrexia of Unknown Origin)

Risk Factors

There are certain factors which make some people more prone to infections, thereby increasing their risk of developing a fever. These include:

  • Age
    Children are at a greater risk of contracting any disease and developing a fever. It can be due to low immunity or coming in contact with affected children at school or play areas. Adolescents can also acquire fever when they come in contact with co-workers, while travelling, etc.
  • Contact
    The pathogens spread by any means like air, water or food or even a vector. Therefore, coming in contact with an affected individual directly or indirectly can increase your risk of getting a fever.
  • Immunity
    People with a weak immune system caused by previous infections or an active pathogen (AIDS) or medications such as corticosteroids can develop fever more frequently.
  • Poor hygiene
    Improper hygiene habits can cause easy entry of pathogens and cause fever.
  • Cancer
    Malignant (cancerous) conditions like lymphoma or leukaemia can cause fever at the onset of the disease or can also be recurrent.

Prevention of fever

In most cases where fever is due to infections, it is possible to prevent the risk of contamination by following certain precautions Some tips to prevent the occurrence of fever are:

Practice good hygiene habits

  • Wash your hands often and teach small children to do it as well, especially before meals, after using the toilet, after spending time with someone who is sick, and after using public transport can help in preventing the spread of infections.
  • Carry a hand sanitizer when you don’t have access to soap and water.
  • Try not to touch your sense organs like eyes, nose or mouth when you feel your hands are dirty and need a thorough washing.
  • Cover your mouth when you sneeze if you have a fever or try to move away if someone is about to sneeze to prevent germs from entering your body.
  • Avoid sharing utensils and water bottles with strangers or people affected by any disease.
  • Avoid travelling to places where you may contract allergies and fever such as hay fever.
  • Control and eradicate breeding sites of mosquitoes in your surroundings to protect yourself from malaria and dengue fever.
  • Get vaccinated with flu vaccines.

Diagnosis of fever

Fever occurs when there is some infection or foreign particle in your body which is not allowing your body to function normally. It is not an illness but is indicative of an underlying infection or other diseases. The underlying cause of fever must be found out so as to begin a specific treatment. If the cause of fever is not clear, then the doctor may take a detailed medical history of the patient and check for different signs which may give a clue to the underlying cause of the fever. Some common tests which a doctor may prescribe are as follows:

  • Blood tests (including differential White blood cell count)
  • Urine examination and culture
  • Throat swabs or mucus sample examination and culture
  • Stool examination and culture
  • X – Rays.

At home, recording the temperature using a thermometer can help in understanding the pattern of fever. There are 4 common sites where thermometer can be placed to measure the body temperature. They are:

  • Axilla (under the armpit)
    The tip of the thermometer is placed under the armpit. Gently press the arm down so that the position of the tip of the thermometer is unchanged. Keep it in position for 1 minute. Generally, the readings from the armpit are 1°C lower than the actual temperature. So, adjust the final readings accordingly and record it for the doctor, if he/she asks.
  • Eardrum
    Tympanic thermometers must be placed in a correct way in case of a child. Earwax can give inaccurate readings though.
  • Oral
    People aged 4 years or older should have their temperature taken by mouth. The tip of the thermometer is kept under the tongue with their mouth closed properly as any mouth opening can cause an inaccurate reading. Keep the thermometer for about a minute.
  • Rectal
    This method is used in children below 3 years of age. It gives an accurate reading. The rectal temperature will be approximately 1°C higher than the body temperature. So, adjust the reading accordingly.
myUpchar doctors after many years of research have created myUpchar Ayurveda Urjas Energy & Power Capsule by using 100% original and pure herbs of Ayurveda. This Ayurvedic medicine has been recommended by our doctors to lakhs of people for problems like physical and sexual weakness and fatigue, with good results.
Power Capsule For Men
₹719  ₹799  10% OFF

Fever treatment

If the fever is mild and non-recurrent, then ideally no treatment is required as it will subside on its own. Fever is a body’s defence mechanism to fight against microorganisms. Microorganisms cannot survive due to temperature fluctuations in the body. There are some simple steps which can be taken to tackle fever or symptoms arising from it. They are:

  • Drink enough fluids which help cool down your body and prevent dehydration.
  • Have easy to digest foods until your fever subsides.
  • Take adequate rest.
  • Take a bath with lukewarm water.
  • Do cold compresses. Apply damp cloth on the forehead to cool down body temperature.
  • Keep a fan on to circulate fresh air.

OTC (over the counter) drugs like paracetamol can be effective in reducing mild fever. But if diagnosis via a blood test reveals an infection then appropriate treatment plan must be followed based on the doctor’s advice. The doctor may prescribe some antibiotics as well as antipyretics to help treat the disease.

Infants may need hospitalisation if fever persists even for a couple of days.

Lifestyle management

Fever is a common symptom that can be caused by any small change in the body’s working pattern due to a foreign substance. Hence, there are no substantial changes that can be made to tackle it. Normally, fever can occur due to stress or overworking of the body or lack of rest. If so, take appropriate measures to eliminate the cause. Take adequate rest and meditate. If a person is prone to allergies like dust or extreme sunlight/heat, which can precipitate changes in the body like cough or heat stroke, try to avoid them. Avoid travelling by public transport as there is an increased risk of catching minor infections.

Managing fever is simple as adequate rest alone may sometimes prove sufficient. Increase intake of fluids to maintain the hydration of the body and to maintain electrolytes level in the blood. Dress lightly, i.e. wear comfortable clothes and keep the room airy. Maintain personal hygiene and in the case of children, be accurate and up to date with the vaccine schedule.

Fever prognosis & complications


The outcome of fever is good if the cause is known and can be treated with an effective treatment plan prescribed by the doctor. But, sometimes fever which is without a known cause (PUO or pyrexia of unknown origin) can prove fatal and has a poor prognosis.


Complications of fever are few and rare. It all depends on the cause and type of fever. If the fever is not treated at the right time, then dehydration is the most common complication. Still, increased fever can cause abnormal brain activity like epilepsy with seizures, coma or even death. Systemic complications can be caused if the cause of fever is related to any particular body system which can affect the body’s working. But, mortality due to fever alone is rare.


  1. American College of Emergency Physicians [Internet] Texas, United States; Fever
  2. DimieOgoina. Fever, fever patterns and diseases called ‘fever’ – A review. Journal of Infection and Public Health Volume 4, Issue 3, August 2011, Pages 108-124. Elsevier B.V. [Internet]
  3. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; When & How to Wash Your Hands
  4. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; Healthy Habits to Help Prevent Flu
  5. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2018. Fever in Adults.
  6. Health Harvard Publishing; Updated: April 30, 2018. Harvard Medical School [Internet]. Fever in adults. Harvard University, Cambridge, Massachusetts.

Medicines for Fever

Medicines listed below are available for Fever. Please note that you should not take any medicines without doctor consultation. Taking any medicine without doctor's consultation can cause serious problems.

Related Articles