Fever in Adults: Causes, Symptoms, and When to Seek Medical Attention

Written By Guest User

Introduction

Fever is one of the most common medical signs and a natural defense mechanism of the body. It is your body's way of telling you that something is wrong. It is typically indicative of the immune system's efforts to combat an invader, frequently an infection. However, there are numerous alternative potential explanations. While a mild (low-grade) fever can often be managed at home, some cases may require urgent medical attention. In this article, we'll break down the causes of fever, common symptoms, and when it's important to seek professional help.

What is a Fever?

Fever is a temporary increase in body temperature above the normal range, often due to illness. There is no single, universally accepted upper limit for normal temperature. Sources cite values between 99.0 and 100.9 °F (37.2 and 38.3 °C) for humans, depending on the location of measurement and certain circumstances, such as the time of day or the method used. In adults, a body temperature above 100.4°F (38°C) is generally considered to be a fever and doesn't tend to rise above 106 to 108°F (41 to 42°C). The Centers for Disease Control and Prevention (CDC) defines a fever as a body temperature of 100.4°F (38°C) or higher, as measured by a thermometer (without specifying the type), combined with symptoms that are warning signs of infectious diseases. In cases where measurement is not possible, a person can still be considered feverish if they feel warm to the touch or report feeling feverish. Other visual signs, such as a flushed face, glassy eyes, or chills, may also indicate a fever.

It is worth noting that the term "fever" is often used quite loosely. Many people may associate the term with feelings of warmth, coldness, or perspiration, even if they have not actually measured their temperature.

Fever is usually grouped by how severe it is, how long it lasts, and what other symptoms it causes, not just the temperature reading on the thermometer. However, here's a basic classification of fever based on temperature readings:

  • Low-Grade Fever: 99.1°F to 100.4°F (37.3°C to 38.0°C)

  • Moderate-Grade Fever: 100.6°F to 102.2°F (38.1°C to 39°C)

  • High-Grade Fever: 102.4°F to 105.8°F (39.1°C to 41°C)

  • Hyperpyrexia: Above 105.8°F (41.°C)

Symptoms Associated with Fever

Fever is frequently accompanied by additional symptoms that can provide insight into its underlying cause. The most commonly observed symptoms include:

  • Chills and Shivering: The body's natural response is to generate heat in order to raise its temperature.

  • Sweating: As your temperature drops, you might start sweating as your body cools down.

  • Headache: Fevers often trigger headaches due to the changes in blood flow and inflammation in the body.

  • Muscle Aches: A common symptom during viral infections like the flu.

  • Fatigue: Fever usually leaves you feeling tired and sluggish as your body devotes energy to fighting off infection.

Common Causes of Fever

Fever can be caused by a wide range of conditions. Below are the most common causes:

  • Infections: These are the leading cause of fever. Common infections that cause fever include the flu, the common cold, urinary tract infections, and gastroenteritis. More serious infections like pneumonia, meningitis, or COVID-19 also often lead to fever. 

  • Heat Exhaustion: If the body overheats for too long in high temperatures, it can cause a fever. This can lead to heatstroke, which is a medical emergency.

  • Inflammatory Conditions: Diseases that cause inflammation in the body, such as rheumatoid arthritis or lupus, can result in fever. In these cases, the fever is a symptom of the underlying autoimmune activity.

  • Medications: Some medications can cause what's known as a drug-induced fever. Antibiotics, blood pressure medications, and anti-seizure drugs can lead to elevated body temperatures in certain individuals.

  • Vaccines: After receiving a vaccine, especially in children but also in adults, a mild fever can occur. This is a natural immune response to the vaccine and typically resolves within a day or two.

  • Cancer: Certain cancers, like leukemia or lymphoma, can cause prolonged or recurrent fevers. This occurs because the immune system becomes activated or because the cancer affects the body’s ability to regulate temperature.

  • Hormonal Imbalances: Conditions like hyperthyroidism (overactive thyroid) can increase the body’s metabolic rate, resulting in a low-grade fever.

When to Seek Medical Attention

While many fevers resolve on their own, there are situations when medical attention is needed. Here are the most important signs that it's time to call a healthcare professional:

  • Persistent High Fever: If your fever remains above 103°F (39.4°C) for more than a day or two, it’s time to consult a doctor.

  • Fever Lasting More Than Three Days: A fever that lasts longer than three days can be a warning sign of an underlying condition.

  • Resistant Fever: The fever does not respond to fever-reducing medication or other cooling measures.

  • Severe Symptoms Along with Fever: If you experience night sweats or swollen lymph nodes, skin rash, cough producing yellow, green, tan, or bloody mucus, difficulty breathing, severe headache, earache, chest pain, persistent vomiting, pain when urinating or back pain, unusual sensitivity to light, confusion, or seizures along with fever, seek medical care.

  • Pregnancy: Pregnant individuals should pay close attention to any changes in their health. High fever can negatively affect fetal development, so it is important to consult a doctor if you experience a fever.

  • Being bitten: Bites from not only ticks but also other animals can be potentially dangerous.

  • Chronic Conditions: You have a known medical condition such as cancer, heart disease (especially heart valve disease), or blood disorders.

  • Compromised Immune System: People with weakened immune systems — such as those undergoing chemotherapy, taking immunosuppressant drugs, or living with HIV — should seek medical attention even for mild fevers. Their bodies may have difficulty fighting off infections that others may easily overcome.

  • Recent Travel: If you’ve recently traveled to areas where diseases like malaria, typhoid, or dengue fever are common, a fever could be a sign of a tropical illness. Seeking medical attention is important to detect and treat these conditions promptly.

  • Fever After Surgery: A fever that develops after surgery could signal an infection at the surgical site or in other parts of the body. In such cases, contact your doctor as soon as possible.

Conclusion

Fever in adults is usually a sign that the body is working to combat an infection or other issue. While many fevers can be managed at home, it’s important to recognize when the situation requires medical attention. Persistent high fevers, severe accompanying symptoms, or underlying health conditions are all red flags that should prompt you to seek professional care.

By understanding the causes and symptoms of fever, you can take appropriate action and ensure that your health is protected.

References

Guest User
Previous

Body Temperature in Children: What’s Normal and When to Be Concerned
Next

What is Normal Body Temperature and How to Accurately Measure It