Chills and Fever: Common Causes, Symptoms & Diagnostic Tests

Experiencing chills and fever together can be uncomfortable and, at times, alarming. You may suddenly start shivering, feel cold despite being covered in blankets, and later notice your body temperature rising. While these symptoms commonly occur together, they are not a disease themselves—they are often signs that your body is responding to an infection or another underlying condition. 

Several illnesses can cause fever with chills, including viral infections, influenza, dengue, malaria, typhoid, urinary tract infections (UTIs), and certain bacterial infections. Since many of these conditions present with similar symptoms, it is not possible to determine the exact cause based on symptoms alone.

Understanding why chills occur, recognising associated symptoms, and knowing when laboratory investigations may be required can help you seek timely medical evaluation.

Why Do Chills and Fever Occur Together

Chills and Fever often occur together because they are both part of your body's immune response.

When your immune system detects an infection, it releases chemicals called pyrogens that signal the brain to temporarily increase the body's internal temperature. As your body tries to reach this new temperature, your muscles repeatedly contract to generate heat, causing shivering or chills.

Once the body reaches the higher temperature, the chills usually stop, and the fever becomes noticeable. As the illness begins to improve, sweating often occurs as the body cools itself back to its normal temperature.

This is why many people experience a cycle of:

• Feeling cold

• Shivering or chills

• Rising body temperature

• Sweating as the fever settles

Although this response is common, not everyone experiences all of these stages.

Different Patterns of Chills and Fever: What Can They Indicate

Although symptoms alone cannot confirm a diagnosis, the pattern of fever and chills may provide useful clues during medical evaluation.

These patterns should only be considered as general guidance. Many illnesses share similar symptoms, which is why laboratory investigations are often recommended to support diagnosis.

Also Read: Possible Reasons for Chills Without a Fever & How to Treat Them

What are the Causes of Chills With Fever

There are numerous causes of chills with fever, ranging from mild and self-limiting to more serious conditions that require prompt medical attention.

• Viral Infections

The common cold, influenza, and COVID-19 are among the most frequent culprits. A sudden fever and chills episode is often the first sign that a viral infection has taken hold, usually accompanied by fatigue, congestion, and a sore throat.

• Bacterial Infections

Urinary tract infections, pneumonia, strep throat, and skin infections like cellulitis can all trigger a high fever with chills. Bacterial infections often cause more intense, prolonged fevers compared to viral illnesses and may require antibiotic treatment.

• Malaria and Vector-Borne Diseases

In regions where mosquito-borne illnesses are common, malaria, dengue, and typhoid fever are important causes to rule out — especially if chills come in cyclical waves alongside sweating and high temperature spikes.

• Gastrointestinal Infections

Food poisoning and stomach infections frequently present as fever chills body aches, along with nausea, vomiting, or diarrhea.

• Inflammatory and Autoimmune Conditions

Less commonly, conditions such as rheumatoid arthritis, lupus, or inflammatory bowel disease can cause recurring low-grade fevers with chills as part of a broader inflammatory response.

• Post-Surgical or Medication-Related Reactions

Certain medications, vaccines, or recent surgical procedures can also trigger transient chills and fever as the immune system responds to a stimulus.

Fever With Shivering: Why It Happens

Fever with shivering  medically known as rigors  occurs when the muscles rapidly contract and relax to produce heat. This is most noticeable during the "cold stage" of a fever, right before your temperature peaks. 

Intense, uncontrollable shivering that comes with a very high temperature can sometimes indicate a more serious bacterial infection, such as sepsis, and should not be ignored, particularly in older adults, young children, or people with weakened immune systems.

Chills Without Fever: What Does It Mean

Interestingly, it's also possible to experience chills without fever. This can happen due to:

• Exposure to cold environments or wet clothing
• Low blood sugar (hypoglycemia)
• Anxiety or panic attacks
• Anemia
• Thyroid disorders, such as hypothyroidism
• The early "pre-fever" phase, before body temperature has actually risen

If chills without an accompanying temperature spike persist or recur frequently, it's worth having them evaluated, since they can sometimes signal an underlying metabolic or hormonal issue rather than an active infection.

Which Tests Help Diagnose Chills and Fever

When chills and fever don't resolve on their own, doctors typically rely on a combination of clinical evaluation and laboratory testing to identify the underlying cause. Common diagnostic tests include:

• Complete Blood Count (CBC)

A Complete Blood Count (CBC) is often one of the first tests recommended for evaluating fever. It checks white blood cell levels to detect signs of infection or inflammation, and can help distinguish between bacterial and viral causes.

• Blood Culture

A Blood Culture may be recommended to Identify bacteria or fungi present in the bloodstream, particularly important if sepsis is suspected.

• C-Reactive Protein (CRP) and ESR Tests

CRP and Erythrocyte Sedimentation Rate (ESR) are inflammatory markers that may be recommended to measure levels of inflammation in the body, useful for tracking infection severity or autoimmune activity.

• Urinalysis and Urine Culture

If fever and chills are associated with burning during urination, frequent urination, or lower abdominal pain, Urine Routine Examination and Urine Culture may be recommended to help diagnose urinary tract infections, a common cause of fever with chills, especially in women and older adults.

• Malaria Test

If fever and chills occur in a cyclical pattern or there is a history of mosquito exposure or travel to a malaria-prone area, your doctor may recommend a Malaria Parasite Test or Rapid Diagnostic Test (RDT). These tests help detect malaria parasites or specific antigens in the blood. 

• Respiratory Infection Tests

If fever and chills are accompanied by symptoms such as cough, sore throat, or difficulty breathing, your doctor may recommend additional investigations to evaluate a possible respiratory infection. Depending on your symptoms, this may include COVID-19, Influenza, or other relevant laboratory tests. 

• Thyroid Function Tests

Although infections are the most common cause of fever and chills, recurrent chills without fever may occasionally require further evaluation for non-infectious conditions. In selected cases, your doctor may recommend a Thyroid Function Test (TFT) to assess thyroid hormone levels. 

Not sure which test you need? Maxlab's fever profile packages bundle the most relevant blood tests together, so you get comprehensive answers in a single visit instead of multiple bookings.

Conclusion

Fever and chills are common symptoms that can occur due to a variety of infections and other underlying conditions. While these symptoms may seem similar across different illnesses, identifying the exact cause often requires a combination of medical evaluation and appropriate laboratory investigations. If your symptoms persist, worsen, or are accompanied by other concerning signs, consult your doctor for further assessment.

If you're experiencing prolonged or severe fever with chills, don't self-diagnose based on symptoms alone  get tested. Maxlab, a trusted pathology lab, offers accurate and timely diagnostic testing, including CBC, blood cultures, CRP/ESR, urinalysis, malaria RDT, and viral/bacterial infection panels, to help you and your doctor pinpoint the exact cause of your fever and chills quickly. With a wide network of collection centers and fast, reliable reporting, Maxlab makes it easy to get the answers you need without added stress.