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Fever refers to a temporary increase in body temperature. Often triggered by an infection, a fever is part of the body’s general immune system reaction. While a fever can cause discomfort for most adults and children, there is no need to worry. However, even a mild fever in infants might indicate a more severe infection.
Typically, fevers resolve within a few days. Many over-the-counter medications can help ease the condition. However, treatment isn’t always necessary, especially if it isn’t associated with discomfort.
By Able Health I Medically reviewed by Dr. Alireza Estedlal
Page last reviewed: February 2024 I Next review due: February 2026
Body temperature can vary among individuals and even at different times throughout the day. The normal body temperature is commonly considered to be 98.6°F (or 37°C). Nonetheless, a temperature of 100°F (37.8°C) and above, when measured orally with a mouth thermometer, is generally defined as a fever.
Based on the underlying cause, additional signs and symptoms associated with a fever might include:
There are many types of thermometers available that you can use to take temperature. These include oral, rectal, forehead (temporal artery), and ear (tympanic).
Rectal and oral thermometers usually provide the most precise readings of core body temperature. While ear and forehead thermometers are convenient, their measurements tend to be less accurate.
If possible, rectal temperatures in infants are considered more reliable. Be sure to provide both the measurement and the thermometer type used when informing your doctor about your temperature.
The natural body temperature involves a balance between heat production and loss. The hypothalamus, often referred to as the body's thermostat, is a region in the brain that regulates this balance. Even when in good health, body temperature can fluctuate slightly throughout the day, typically lower in the morning and rising higher by late afternoon or evening.
When the immune system detects illness, the hypothalamus raises body temperature to trigger complex processes that generate more heat and limit heat loss. For example, shivering is a mechanism the body uses to create heat. So, wrapping yourself in a blanket when feeling cold helps your body conserve heat.
Fevers lower than 104°F (40°C) associated with viral infections like the flu can assist the body’s immune system in fighting illness and are usually not dangerous.
Possible causes of fever or high body temperature include:
Children aged six months to five years tend to be more susceptible to febrile seizures (seizures caused by fever). Approximately one-third of minors who experience a febrile seizure will likely have another, mostly within one year.
Febrile seizures can be characterised by unconsciousness, limb shaking on both sides of the body, body rigidity, and eye-rolling. While it can be frightening, most febrile seizures do not cause long-term effects.
In the event of a febrile seizure, do the following:
If emergency care isn’t necessary, consult your child’s physician promptly for further assessment.
You can book an appointment with a private GP today for only £20*.
Book an appointmentYou can prevent or reduce the risk of fevers by minimising contact with infectious illnesses. Consider the following preventive measures:
To evaluate a fever, your doctor will likely:
For infants, particularly those who are two months old and younger, a fever can be a sign of a serious illness. Therefore, the baby may require hospitalisation for further tests and treatment.
When a fever persists for over three weeks (continuously or intermittently) and the cause is unclear, it is normally categorised as a fever of unknown origin. In such cases, you may be referred to a specialist in one or several medical fields for additional assessment and tests.
To address low-grade fevers, doctors might advise against using medicine to reduce body temperature. This is because mild fevers can help combat the harmful microbes causing infection in the body. However, fevers over 102°F (38.9°C) can be uncomfortable and usually require treatment.
If you have a high fever or feel uncomfortable, your doctor may suggest using non-prescription medications like paracetamol (Calpol) and ibuprofen (Nurofen).
It’s important to follow the dosage instructions on the label or as your provider advises. Ensure that you do not exceed the recommended doses. Prolonged use or high doses of ibuprofen or paracetamol can result in kidney or liver damage, and severe cases of overdose may also be life-threatening. Additionally, never give aspirin to children, as it can cause a rare but potentially fatal condition called Reye’s syndrome.
While these over-the-counter medications can help reduce your temperature, you might still experience a mild fever. It can take about one to two hours for the medication to take effect. If your fever does not improve after using medication, contact your provider.
The doctor can recommend additional medications depending on the underlying cause of your fever. Addressing the root of your illness can help alleviate symptoms as well as the fever.
Babies, particularly those under two months, may require hospitalisation for further tests and treatment. A fever in such a young child may indicate a severe infection requiring intravenous (IV) medication and continuous monitoring.
To ensure that you or your baby are comfortable while experiencing a fever, you can try the following self-care measures:
You can make an appointment with a paediatrician, family doctor, or another healthcare provider. The following information will assist you in preparing for your visit and understanding what to expect:
Some fundamental questions about fever to consider asking your doctor include:
Feel free to ask any additional questions that arise during the visit.
Be prepared to answer the following questions:
Being prepared with this information will help your healthcare provider diagnose and treat your fever more effectively.
A fever alone shouldn’t be a cause for concern or a reason to see a specialist. However, there are certain situations where you need to seek medical attention for yourself or your child.
Fevers in infants and toddlers are particularly concerning. Therefore, it’s important to contact a physician if your baby is:
If a child develops a fever and appears alert and responsive, there’s usually no cause for alarm. This implies that your child makes eye contact, reacts to facial expressions and voices, plays actively, and drinks fluids.
However, you should contact your child’s doctor if they:
Consult your child’s provider for advice in special situations, such as if they have a pre-existing condition or immune system issues.
Contact your provider if your body temperature reaches 103°F (39.4°C) or above. Also, seek medical care immediately if you experience any of the following signs along with a fever: