Fever in the clinic: what doctors assess and what medicines may be used

1. Conditions that can cause fever

• Viral infections: common cold, influenza, COVID-19, dengue, viral gastroenteritis
• Bacterial infections: throat infection, pneumonia, urinary tract infection, skin infection, typhoid, tuberculosis
• Vector-borne infections: malaria, dengue, chikungunya, leptospirosis, depending on travel and local outbreaks
• Inflammatory or autoimmune disease: for example lupus or rheumatoid disease
• Drug reaction, clot, cancer, or other less common causes, especially if fever is persistent or unexplained

2. Types of fever

By duration

• Acute fever: under 7 days, often viral or a short bacterial illness.
• Subacute fever: roughly 1-2 weeks.
• Persistent/prolonged fever: over 2 weeks, needs a more structured evaluation.
• Fever of unknown origin: prolonged documented fever after an appropriate initial assessment has not found a cause.

By temperature pattern

• Intermittent: temperature returns to normal between spikes.
• Remittent: fluctuates but does not return fully to normal.
• Continuous/sustained: remains elevated with little variation.
• Relapsing/recurrent: fever-free intervals followed by new episodes.

3. Medicines commonly used for fever

A. Fever reducers, also called antipyretics

1. Paracetamol / acetaminophen
   • Common first option for fever and body aches.
   • Often preferred when NSAIDs are unsuitable, such as some people with stomach-ulcer risk.
   • Must be used carefully in liver disease, heavy alcohol use, or when taking other cold/flu products that also contain paracetamol.
   • Taking too much can cause severe liver failure.
2. Ibuprofen
   • Reduces fever, inflammation, and pain.
   • Avoid or use only under clinician advice with kidney disease, dehydration, peptic ulcer/bleeding history, heart failure, anticoagulants, or some asthma.
   • Avoid in suspected dengue unless a clinician specifically advises otherwise because bleeding risk can be a concern.
   • Usually avoided in pregnancy, particularly later pregnancy.
3. Naproxen or other NSAIDs
   • Occasionally used for pain and fever in selected adults, but not usually necessary as a first choice.
   • Similar stomach, kidney, bleeding, and cardiovascular cautions apply.

B. Medicines that treat the cause

• Antibiotics: only for likely or confirmed bacterial infection, such as bacterial pneumonia, UTI, strep throat, or certain enteric infections. They do not treat viral fever.
• Antivirals: for selected people with influenza or COVID-19, particularly higher-risk patients, and they work best when started early. The CDC respiratory-virus guidance advises contacting a clinician promptly if a higher-risk person develops respiratory symptoms.
• Antimalarial medicines: only after appropriate assessment/testing or strong clinical suspicion in endemic/travel settings.
• Specific therapy for dengue, viral infections, and many other illnesses is usually fluids, monitoring, and symptom relief rather than antibiotics.

4. Important safety points

• The objective is comfort and hydration, not forcing the temperature fully normal. Medical texts note that antipyretics are generally used when fever causes significant discomfort or may be harmful, rather than simply to normalize every raised temperature.
• Drink fluids if allowed, rest, and wear light clothing.
• Do not give aspirin to children or teenagers with fever from a viral illness because of the risk of Reye syndrome. The CDC flu guidance specifically warns against it.
• Do not use leftover antibiotics or someone else’s prescription.
• Children need weight-based dosing, ideally measured with an oral syringe, not a kitchen spoon. The AAP dosing guidance advises clinician guidance for very young children and careful avoidance of multi-ingredient products.

Seek urgent care now if fever is associated with

• Trouble breathing, blue lips, chest pain, oxygen low
• Confusion, unusual sleepiness, fainting, seizure
• Severe headache with neck stiffness
• Purple/non-blanching rash
• Severe dehydration, no urine, persistent vomiting
• Severe abdominal pain
• Low blood pressure, cold clammy skin, rapidly worsening illness
• Fever after chemotherapy, transplant, or in significant immune suppression
• A baby under 3 months with a temperature of 38°C or above
• Fever with pregnancy, especially if unwell
• Suspected malaria, severe dengue warning signs, or recent high-risk travel