## Overview
Chills — classified under ICD-10 code R68.83 — are episodes of involuntary shivering or shaking accompanied by a sensation of coldness, often (but not always) preceding or accompanying a fever. The term "rigors" is used clinically to describe severe, uncontrollable shaking episodes, while milder chills may present as goosebumps (piloerection) and a subjective feeling of being cold despite a normal ambient temperature.
Chills are among the most common symptoms prompting online health searches and primary-care visits. Population-based surveys suggest that the vast majority of adults experience chills at least once per year, most often in association with acute viral infections [1]. Chills are the body's thermogenic response — skeletal-muscle contractions generate heat to raise core body temperature toward a new, elevated set point dictated by pyrogenic cytokines acting on the hypothalamus [2].
People search for information about chills for several reasons: to determine whether their chills indicate a serious infection, to distinguish chills with fever from chills without fever, to find safe home remedies, and to decide whether they need medical attention. This article provides an evidence-based overview of the causes, evaluation, and management of chills for general adults, while emphasizing the importance of professional medical assessment when warning signs are present.
**Important:** This article is for educational purposes only and does not replace individualized medical advice. Always consult a qualified healthcare provider for diagnosis and treatment.
## Common Causes
Chills arise when the hypothalamic thermoregulatory set point is elevated (as in fever) or when the body attempts to conserve or generate heat in response to cold exposure. Below are the most common causes, ranked roughly by frequency.
### 1. Viral Infections (Most Common)
Acute respiratory infections — including influenza, COVID-19, rhinovirus, and respiratory syncytial virus (RSV) — are the leading cause of chills in adults. Viral pathogen-associated molecular patterns (PAMPs) trigger innate immune cells to release pyrogens such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α). These cytokines stimulate prostaglandin E2 (PGE2) synthesis in the hypothalamic preoptic area, raising the thermoregulatory set point [2]. The body then perceives its current temperature as "too cold," initiating shivering thermogenesis and peripheral vasoconstriction.
### 2. Bacterial Infections
Urinary tract infections (UTIs), pneumonia, skin and soft-tissue infections (cellulitis), and intra-abdominal infections frequently produce chills — sometimes with rigors. Bacteremia and sepsis are particularly associated with shaking chills; a prospective study found that rigors in hospitalized patients had a positive predictive value of approximately 15–20% for bacteremia [3]. Gram-negative bacteremia classically produces more pronounced rigors due to endotoxin (lipopolysaccharide) release.
### 3. Environmental Cold Exposure and Hypothermia
Exposure to cold ambient temperatures or cold water immersion triggers shivering as a primary thermoregulatory mechanism. When core body temperature drops below approximately 36.0 °C (96.8 °F), shivering intensifies. In moderate-to-severe hypothermia (core temperature below 32 °C / 89.6 °F), shivering may paradoxically cease, which is a dangerous sign.
### 4. Drug and Transfusion Reactions
Certain medications — including amphotericin B, bleomycin, interferon-alpha, monoclonal antibodies, and some biologics — are well-known to cause infusion-related chills and rigors. Febrile non-hemolytic transfusion reactions (FNHTR) are among the most common transfusion reactions, occurring in approximately 1–3% of red blood cell transfusions, and typically present with chills and low-grade fever [4].
### 5. Inflammatory and Autoimmune Conditions
Systemic lupus erythematosus (SLE), rheumatoid arthritis, adult-onset Still disease, and vasculitides may produce intermittent fevers with chills during disease flares. Cytokine-mediated pyrexia follows a mechanism similar to infection-driven fever.
### 6. Malignancy
Lymphomas (particularly Hodgkin lymphoma), leukemias, and renal cell carcinoma may present with recurrent fevers and chills — sometimes as "B symptoms" (fever, drenching night sweats, unintentional weight loss). Tumor-derived pyrogens and paraneoplastic cytokine release are the underlying mechanisms.
### 7. Endocrine Causes
Hypothyroidism can cause cold intolerance and chills due to reduced basal metabolic rate. Hypoglycemia may trigger shivering and chills via sympathoadrenal activation. Adrenal insufficiency and hypopituitarism may also present with cold intolerance.
### 8. Anxiety and Panic Disorders
Autonomic nervous system activation during panic attacks or severe anxiety may produce chills, goosebumps, and trembling in the absence of fever or infection. These episodes are generally self-limited and associated with other autonomic symptoms such as tachycardia, diaphoresis, and hyperventilation.
### 9. Post-Anesthesia Shivering
Shivering occurs in 20–70% of patients recovering from general or neuraxial anesthesia, resulting from anesthetic-induced impairment of central thermoregulation and redistribution hypothermia [5].
## RED FLAGS
Seek **immediate medical attention** (call emergency services or go to the nearest emergency department) if chills are accompanied by any of the following:
- **High fever (≥ 39.4 °C / 103 °F) that does not respond to antipyretics** — may indicate serious bacterial infection or sepsis
- **Altered mental status, confusion, or difficulty staying awake** — possible sepsis, meningitis, or encephalitis
- **Severe headache with neck stiffness and light sensitivity** — classic triad of meningitis
- **Rapid breathing (> 22 breaths/min) or shortness of breath at rest** — may indicate pneumonia, pulmonary embolism, or sepsis
- **Heart rate > 100 bpm at rest with low blood pressure (systolic < 90 mmHg)** — signs of septic shock [6]
- **Petechial or purpuric rash (small, non-blanching red/purple spots)** — may indicate meningococcemia or disseminated intravascular coagulation (DIC)
- **Rigors following recent surgery, hospitalization, or invasive procedure** — may indicate healthcare-associated infection or surgical-site infection
- **Immunocompromised state** (chemotherapy, HIV/AIDS, organ transplant, chronic corticosteroid use) with any fever and chills — infection may progress rapidly
- **Recent travel to malaria-endemic region** with cyclical fevers and chills — requires urgent thick and thin blood smear evaluation
- **Inability to keep fluids down** with signs of dehydration (dry mouth, minimal urine output, dizziness on standing)
- **Severe abdominal pain with fever and chills** — possible appendicitis, cholangitis, or peritonitis
## Self-Care at Home
When chills are associated with a mild, self-limited illness (such as a common cold or mild flu) and no red flags are present, the following evidence-based self-care measures may help:
### Hydration
Maintain adequate fluid intake. Fever increases insensible water losses through perspiration and increased respiratory rate. Water, clear broths, oral rehydration solutions, and herbal teas are all appropriate choices. The goal is to maintain clear-to-pale-yellow urine output.
### Rest and Temperature Regulation
Dress in light, breathable layers that can be added or removed as chills and sweating alternate. Use light blankets during chills episodes and remove them when sweating begins. Rest allows the immune system to allocate energy toward pathogen clearance.
### Warm Fluids
Warm (not hot) beverages — including broth, herbal tea, and warm water with honey and lemon — may provide subjective comfort during chills. Honey has demonstrated modest antimicrobial and soothing properties for upper respiratory symptoms in some studies [7].
### Lukewarm Baths or Compresses
A lukewarm (not cold) bath or sponge bath may help regulate body temperature when fever is present. Avoid cold water or ice baths, which can worsen shivering and paradoxically raise core temperature by triggering intense peripheral vasoconstriction.
### Nutrition
Eat when appetite allows. Nutrient-dense, easily digestible foods (soups, fruits, whole grains) support immune function. There is no strong evidence for "starving a fever" — adequate caloric intake is generally beneficial during acute illness.
### Environmental Comfort
Maintain a comfortable room temperature (approximately 20–22 °C / 68–72 °F). Avoid drafts, but ensure adequate ventilation. Humidified air may ease respiratory symptoms that accompany infectious chills.
## OTC Medications That Help
Over-the-counter (OTC) medications primarily target the fever that underlies most episodes of chills. By lowering the hypothalamic set point back to normal, antipyretics reduce the drive to shiver.
| Class | Example | Adult Dose | Notes |
|-------|---------|------------|-------|
| **Analgesic/Antipyretic** | Acetaminophen (paracetamol) | 500–1000 mg every 4–6 hours; max 3000 mg/day (or 2000 mg/day with liver risk factors) | Avoid in severe hepatic impairment. FDA warns against exceeding 3000 mg/day for OTC use. Does not cause GI bleeding. Generally considered the first-line OTC antipyretic [8]. |
| **NSAID** | Ibuprofen | 200–400 mg every 4–6 hours; max 1200 mg/day (OTC) | Avoid in renal impairment, active GI bleeding, third trimester of pregnancy, and aspirin-exacerbated respiratory disease. Take with food. Effective antipyretic and analgesic. |
| **NSAID** | Naproxen sodium | 220 mg every 8–12 hours; max 660 mg/day (OTC) | Longer duration of action than ibuprofen. Same NSAID precautions apply. May be preferred when less-frequent dosing is desired. |
| **NSAID** | Aspirin (acetylsalicylic acid) | 325–650 mg every 4–6 hours; max 4000 mg/day | Effective antipyretic but associated with higher GI risk. **Contraindicated in children and adolescents under 18** due to risk of Reye syndrome. Avoid in patients on anticoagulants. |
| **Combination products** | Acetaminophen + phenylephrine + dextromethorphan (e.g., multi-symptom cold formulas) | Per package labeling | Useful when chills accompany cold/flu with congestion and cough. Watch for duplicate acetaminophen dosing across products. |
**Key considerations:**
- Do not combine multiple NSAID products.
- Alternating acetaminophen and ibuprofen every 3–4 hours is sometimes used in practice to manage persistent fever, though evidence for superiority over monotherapy is limited.
- Always read labels carefully to avoid exceeding maximum daily doses, especially with combination products containing acetaminophen.
## Prescription Options
Prescription treatment for chills is directed at the underlying cause rather than the symptom itself. Below are common prescription classes organized by indication.
| Class | Examples | When Used | Who Prescribes |
|-------|----------|-----------|----------------|
| **Antibiotics (oral)** | Amoxicillin-clavulanate, azithromycin, ciprofloxacin, trimethoprim-sulfamethoxazole | Bacterial infections (UTI, pneumonia, sinusitis, cellulitis) confirmed or strongly suspected clinically | Primary care physician, urgent care provider |
| **Antibiotics (IV)** | Ceftriaxone, piperacillin-tazobactam, vancomycin, meropenem | Sepsis, severe pneumonia, pyelonephritis, febrile neutropenia | Emergency physician, hospitalist, infectious disease specialist |
| **Antivirals** | Oseltamivir (Tamiflu), baloxavir (Xofluza), nirmatrelvir-ritonavir (Paxlovid) | Influenza (within 48 hours of symptom onset) or COVID-19 in high-risk individuals | Primary care physician, urgent care, telemedicine |
| **Antimalarials** | Chloroquine, artemether-lumefantrine, atovaquone-proguanil | Confirmed or suspected malaria | Infectious disease specialist, travel medicine clinic, emergency physician |
| **Corticosteroids** | Prednisone, methylprednisolone, dexamethasone | Autoimmune flares, severe inflammatory conditions, adrenal insufficiency | Rheumatologist, endocrinologist, primary care |
| **Thyroid hormone** | Levothyroxine | Hypothyroidism causing cold intolerance and chills | Endocrinologist, primary care physician |
| **Anti-shivering agents** | Meperidine (pethidine), dexmedetomidine | Post-anesthesia shivering in perioperative setting | Anesthesiologist (hospital use only) |
| **Antipyretics (prescription-strength)** | Indomethacin, ketorolac | Refractory fever not responding to OTC antipyretics, neoplastic fever | Hospitalist, oncologist |
**Note:** Antibiotics should only be prescribed when a bacterial infection is confirmed or strongly suspected. Inappropriate antibiotic use contributes to antimicrobial resistance — a major global public-health concern.
## Lab Tests Typically Ordered
When chills prompt a medical evaluation, clinicians select laboratory and diagnostic tests based on the clinical picture. Common tests include:
| Test | Rationale |
|------|-----------|
| **Complete blood count (CBC) with differential** ([more info](/tests/complete-blood-count)) | Elevated white blood cell (WBC) count suggests infection; left shift (increased bands/immature neutrophils) points to bacterial infection; low WBC may indicate viral infection or immunosuppression |
| **C-reactive protein (CRP)** ([more info](/tests/c-reactive-protein)) | Non-specific marker of inflammation; levels > 50 mg/L generally suggest bacterial rather than viral infection |
| **Procalcitonin** ([more info](/tests/procalcitonin)) | More specific than CRP for bacterial infection; levels > 0.5 ng/mL suggest bacterial etiology and may guide antibiotic decisions |
| **Blood cultures (×2 sets)** ([more info](/tests/blood-cultures)) | Essential when bacteremia or sepsis is suspected; should be drawn before antibiotics are started |
| **Urinalysis and urine culture** ([more info](/tests/urinalysis)) | Evaluates for urinary tract infection as a source of fever and chills |
| **Basic metabolic panel (BMP)** ([more info](/tests/basic-metabolic-panel)) | Assesses renal function, electrolytes, and glucose; helps evaluate hydration status and detect organ dysfunction |
| **Liver function tests (LFTs)** ([more info](/tests/liver-function-tests)) | Evaluates hepatobiliary causes of fever (hepatitis, cholangitis, liver abscess) |
| **Lactate level** ([more info](/tests/lactate)) | Elevated lactate (> 2 mmol/L) may indicate tissue hypoperfusion and is a key criterion in sepsis assessment [6] |
| **Chest X-ray** | Evaluates for pneumonia, pleural effusion, or other pulmonary pathology when respiratory symptoms accompany chills |
| **Thick and thin blood smears** | Required when malaria is suspected (travel history to endemic region with cyclical fevers and chills) |
| **Thyroid-stimulating hormone (TSH)** ([more info](/tests/tsh)) | Screens for hypothyroidism in patients with chronic cold intolerance and chills without infectious symptoms |
| **Blood glucose** ([more info](/tests/blood-glucose)) | Rules out hypoglycemia as a cause of shivering and autonomic symptoms |
## Special Populations
### Children
Chills and fever in children are most commonly caused by self-limited viral infections. However, febrile infants under 3 months of age require urgent medical evaluation and often empiric antibiotics, as the risk of serious bacterial infection (SBI) is higher and clinical assessment is less reliable in this age group.
- **Acetaminophen** may be used in infants ≥ 3 months (dose: per manufacturer guidelines based on weight; consult a pediatrician for exact dosing).
- **Ibuprofen** may be used in infants ≥ 6 months (dose: per manufacturer guidelines based on weight; consult a pediatrician for exact dosing).
- **Aspirin is contraindicated** in children and adolescents under 18 due to the risk of Reye syndrome, a rare but potentially fatal condition affecting the liver and brain [9].
- The American Academy of Pediatrics (AAP) emphasizes that the primary goal of treating fever in children is to improve comfort, not to normalize temperature [9]. Parents and caregivers should not "chase" a specific number on the thermometer.
- **Do not give OTC cough/cold combination products to children under 4 years** without explicit guidance from a healthcare provider.
### Pregnancy
- **Acetaminophen** is generally considered the safest antipyretic during pregnancy (all trimesters) and is the preferred first-line agent. However, prolonged use should be avoided, and the lowest effective dose for the shortest duration is advised.
- **NSAIDs (ibuprofen, naproxen)** should generally be avoided in pregnancy, particularly after 20 weeks of gestation. The FDA issued a safety communication in 2020 warning that NSAID use at 20 weeks or later can cause rare but serious kidney problems in the unborn baby, resulting in low amniotic fluid [10]. NSAIDs are **contraindicated in the third trimester** due to risk of premature closure of the ductus arteriosus.
- **Aspirin** at analgesic/antipyretic doses is generally avoided in pregnancy. Low-dose aspirin (81 mg) may be used for pre-eclampsia prevention under obstetric guidance, but this is a different indication.
- Fever itself during the first trimester has been associated with a modestly increased risk of neural tube defects in some studies, which underscores the importance of appropriate antipyretic use during pregnancy.
- Pregnant individuals with fever and chills should contact their obstetric provider promptly, as infections such as pyelonephritis, chorioamnionitis, and listeriosis require timely treatment.
### Elderly (≥ 65 years)
- Older adults may have a **blunted febrile response**, meaning they may experience chills with only a modest temperature elevation or even a normal temperature. A temperature of 37.8 °C (100 °F) in an elderly patient may represent a clinically significant fever.
- The threshold for evaluation should be lower in elderly patients, as the risk of serious bacterial infection, sepsis, and complications is higher.
- **Renal function declines with age**, making NSAID use riskier (increased risk of acute kidney injury, GI bleeding, and cardiovascular events). Acetaminophen is generally preferred, with dose adjustment if hepatic function is impaired.
- Polypharmacy is common in this population — always check for drug interactions before recommending OTC medications.
- Dehydration develops more quickly in elderly patients during febrile illness due to decreased thirst perception and reduced renal concentrating ability.
### Athletes
- Athletes may experience chills during or after intense exercise due to exercise-induced hypothermia (particularly in cold-weather or water sports), post-exercise immunosuppression (the "open window" theory), or exercise-associated hyponatremia.
- **Exertional heat illness** can paradoxically present with chills when the body's thermoregulatory mechanisms become dysregulated. An athlete with chills during or after intense exercise in heat should be evaluated for heat stroke.
- NSAIDs should be used cautiously in athletes, particularly during endurance events, as they may increase the risk of acute kidney injury in the setting of dehydration and high renal blood flow demands.
- Athletes should not "push through" training when experiencing chills with fever, as exercise during systemic infection increases the risk of myocarditis, particularly with certain viral infections (e.g., influenza, COVID-19).
## When to Escalate
Use the following thresholds to determine the appropriate level of care:
### Self-Care Is Appropriate When:
- Chills are mild and associated with a known cold or mild flu
- Temperature is below 38.9 °C (102 °F) and responds to OTC antipyretics
- The individual is able to maintain oral hydration
- No red-flag symptoms are present
- Symptoms have been present for fewer than 3 days
### Same-Day Primary Care (GP) Visit When:
- Fever and chills persist beyond 3 days despite OTC treatment
- Fever is between 38.9 °C and 39.4 °C (102–103 °F) in an otherwise healthy adult
- Urinary symptoms (dysuria, frequency, flank pain) accompany chills — suggests UTI or pyelonephritis
- Productive cough with colored sputum and chills — possible bacterial pneumonia
- New or worsening rash with fever
- Chills are recurrent without an obvious cause
### Urgent Care (Same Day) When:
- Fever ≥ 39.4 °C (103 °F) that does not improve with acetaminophen or ibuprofen
- Significant body aches, fatigue, and chills in the setting of possible influenza (for timely antiviral initiation within 48 hours of symptom onset)
- Moderate dehydration (reduced urine output, dry mucous membranes, lightheadedness)
- Chills following a recent minor procedure or dental work
- Symptoms worsening after an initial period of improvement ("second sick")
### Emergency Department / Call 911 When:
- Any red-flag symptom listed in the RED FLAGS section above
- Temperature ≥ 40 °C (104 °F) with rigors and signs of systemic illness
- Suspected sepsis: fever/hypothermia + tachycardia + tachypnea + altered mental status + hypotension [6]
- Immunocompromised patient with any fever and chills
- Infant under 3 months with rectal temperature ≥ 38.0 °C (100.4 °F)
- Chills with severe abdominal pain, jaundice, or signs of peritonitis (rigid abdomen)
- Return from malaria-endemic region with cyclical fevers
- Signs of anaphylaxis (chills with urticaria, angioedema, hypotension after medication or allergen exposure)
## References
[1] Eccles R. Understanding the symptoms of the common cold and influenza. Lancet Infect Dis. 2005;5(11):718-725. PMID:16253889.
[2] Nakamura K. Central circuitries for body temperature regulation and fever. Am J Physiol Regul Integr Comp Physiol. 2011;301(5):R1207-R1228. PMID:21900642.
[3] Tokuda Y, Miyasato H, Stein GH, Schifman RB. The degree of chills for risk of bacteremia in acute febrile illness. Am J Med. 2005;118(12):1417. PMID:16378800.
[4] Hendrickson JE, Hillyer CD. Noninfectious serious hazards of transfusion. Anesth Analg. 2009;108(3):759-769. PMID:19224780.
[5] Sessler DI. Perioperative thermoregulation and heat balance. Lancet. 2016;387(10038):2655-2664. PMID:26775126.
[6] Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):801-810. PMID:26903338.
[7] Abuelgasim H, Albury C, Lee J. Effectiveness of honey for symptomatic relief in upper respiratory tract infections: a systematic review and meta-analysis. BMJ Evid Based Med. 2021;26(2):57-64. PMID:32817011.
[8] U.S. Food and Drug Administration. Acetaminophen information. FDA Drug Safety Communication. Updated 2023. Available at: https://www.fda.gov/drugs/information-drug-class/acetaminophen-information.
[9] Sullivan JE, Farrar HC; Section on Clinical Pharmacology and Therapeutics, Committee on Drugs. Fever and antipyretic use in children. Pediatrics. 2011;127(3):580-587. PMID:21357332.
[10] U.S. Food and Drug Administration. FDA recommends avoiding use of NSAIDs in pregnancy at 20 weeks or later. FDA Drug Safety Communication. October 2020. Available at: https://www.fda.gov/drugs/drug-safety-and-availability/fda-recommends-avoiding-use-nsaids-pregnancy-20-weeks-or-later.
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*Disclaimer: This article is provided for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition. If you think you may have a medical emergency, call your doctor or emergency services immediately.*
