Chronic Low-Grade Fever at Night: Common Causes and What You Should Know

Experiencing a persistent low-grade fever, especially during the evening or nighttime, can be both confusing and concerning. While occasional fluctuations in body temperature are normal, recurring low fevers—typically defined as a temperature between 98.6°F (37°C) and 100.4°F (38°C)—may signal an underlying health condition. These mild but consistent elevations in body heat often go unnoticed during the day but become more apparent at night due to natural circadian rhythms and reduced distractions. Understanding the potential causes is essential for timely diagnosis and effective treatment.

Potential Medical Conditions Linked to Nighttime Low-Grade Fevers

Nighttime low fevers aren't always caused by simple infections. In fact, they can stem from a wide range of physiological imbalances and chronic diseases. Below are some of the most common medical explanations behind this symptom, backed by clinical observations and research.

1. Autonomic Nervous System Dysfunction

Stress, anxiety, or emotional trauma can overstimulate the brain's cortex, disrupting the autonomic nervous system—the part responsible for regulating involuntary functions like heart rate, digestion, and body temperature. When this system becomes unbalanced, it may lead to persistent low-grade fevers, particularly in the evening. Patients might also experience fatigue, insomnia, or palpitations. Treatment typically includes nerve-stabilizing medications such as oryzanol tablets or vitamin B12 supplements, prescribed under medical supervision to restore neurological balance.

2. Viral Infections

Certain viral infections—including cytomegalovirus (CMV), Coxsackievirus, and herpes B virus—can trigger prolonged low-level inflammation in the body. For example, CMV infection leads to continuous release of inflammatory mediators that disrupt internal homeostasis, resulting in recurrent low fevers, especially at night. Additional symptoms may include coughing, sore throat, and general malaise. Antiviral therapies such as foscarnet sodium injection are commonly used under a physician's guidance to manage these infections effectively.

3. Pulmonary Tuberculosis

Tuberculosis (TB), caused by Mycobacterium tuberculosis, frequently presents with night fevers, along with symptoms like chronic cough, weight loss, and hemoptysis (coughing up blood). The immune system tends to weaken during nighttime hours, allowing latent TB activity to manifest as a low-grade fever. Early morning cortisol surges help suppress inflammation during the day, masking symptoms until evening. Standard treatment involves a multi-drug regimen including isoniazid and rifampicin, administered over several months to fully eradicate the bacteria.

4. Lymph Node Tuberculosis (Scrofula)

When tuberculosis spreads to the lymph nodes, it causes swelling, tenderness, and systemic effects such as intermittent fevers, night sweats, and pallor. The bacterial toxins interfere with the central nervous system and autonomic regulation, contributing to elevated nighttime temperatures. Diagnosis usually requires imaging and biopsy confirmation. Therapeutic options include pyrazinamide and ethambutol hydrochloride, which penetrate infected tissues and support long-term recovery when taken consistently.

5. Rheumatoid Arthritis

This autoimmune disorder doesn't just affect joints—it can cause systemic inflammation leading to persistent low fevers. As joint damage progresses and immune defenses decline, patients become more susceptible to secondary infections, further exacerbating fever episodes. Swelling, stiffness, and fatigue often accompany the thermal changes. Disease-modifying antirheumatic drugs (DMARDs) like methotrexate or sulfasalazine enteric-coated tablets are key in controlling disease progression and reducing inflammatory markers.

6. Dermatomyositis

A rare inflammatory disease affecting skin and muscle tissue, dermatomyositis stems from immune dysregulation. This malfunction increases vulnerability to various infections, which in turn can cause recurring low-grade fevers. Patients may also develop rashes, muscle weakness, and difficulty swallowing. Corticosteroids such as prednisone acetate or methylprednisolone are standard treatments aimed at suppressing abnormal immune responses and alleviating systemic symptoms.

7. Systemic Lupus Erythematosus (SLE)

In SLE, the body produces autoantibodies that attack its own cells, particularly red blood cells. This destruction releases endogenous pyrogens—internal fever-inducing substances—that contribute to chronic low fevers. Immune suppression also raises the risk of concurrent infections. Alongside fatigue and joint pain, night fevers are a hallmark sign. Management typically involves immunosuppressive therapy using agents like prednisone or methylprednisolone to stabilize immune function and prevent organ damage.

8. HIV/AIDS

HIV infection compromises the immune system and disrupts thermoregulation, making low-grade fevers—especially at night—a common early and late-stage symptom. Other signs include unexplained weight loss, swollen lymph nodes, and recurrent infections. With proper antiretroviral therapy (ART), such as tenofovir alafenamide and lamivudine, patients can achieve viral suppression, improve immunity, and reduce fever episodes significantly.

9. Leukemia

Blood cancers like leukemia alter white blood cell production and function. Chemotherapy, while necessary, can destroy healthy leukocytes, triggering inflammatory responses and persistent low fevers. Symptoms such as bruising, nosebleeds, and gum bleeding often accompany the fever. Targeted therapies like imatinib mesylate or nilotinib capsules help control cancer growth and minimize complications, including fever-related discomfort.

10. Malignant Tumors and Cancer

Cancer cells metabolize rapidly, consuming large amounts of energy and generating excess heat as a byproduct. This hypermetabolic state often results in chronic low fevers, particularly noticeable at night. Patients may also experience unintentional weight loss, night sweats, and progressive weakness. Depending on the tumor type and stage, treatment may involve surgical removal, chemotherapy, radiation, or immunotherapy—all designed to halt disease progression and relieve systemic symptoms.

Other Conditions That May Cause Recurrent Low Fevers

Beyond the major illnesses listed above, several other disorders can present with similar patterns of nocturnal temperature elevation. These include:

• Intestinal tuberculosis: Similar to pulmonary TB but affecting the gastrointestinal tract; treated with streptomycin, isoniazid, and rifampicin.
• Typhoid fever: A bacterial infection causing prolonged low-grade fever, abdominal pain, and constipation or diarrhea.
• Rheumatic arthritis: Post-streptococcal inflammatory condition affecting joints and heart valves.
• Sjögren's syndrome: An autoimmune disease causing dry eyes and mouth, often associated with fatigue and low fevers.
• Adrenal cortical hyperactivity: Overproduction of cortisol can disrupt immune and metabolic functions, leading to subtle temperature changes.

When to Seek Medical Attention

If you're regularly experiencing unexplained low-grade fevers—particularly if they occur at night and persist for more than two weeks—it's crucial to consult a healthcare provider. A visit to an internal medicine specialist can help identify the root cause through diagnostic tests such as:

• Complete blood count (CBC)
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
• Tuberculosis testing (sputum culture, interferon-gamma release assays)
• Autoimmune panels (ANA, RF)
• HIV screening
• Imaging studies (chest X-ray, CT scan)

Early detection improves outcomes across all conditions—from treatable infections to complex autoimmune diseases. Don't ignore your body's signals. Persistent nighttime fevers are not something to dismiss as "just stress" or "a weak immune system." They could be your body's way of alerting you to a deeper issue that needs attention.

In conclusion, chronic low-grade fever at night should never be overlooked. Whether linked to infection, autoimmune disease, or malignancy, identifying the underlying cause is the first step toward healing. Always seek professional evaluation and follow evidence-based treatment plans tailored to your specific diagnosis.