High temperature (fever) in adults

A fever in adults is typically defined as a temporary increase in body temperature above the normal range of 36.1°C to 37.2°C (97°F to 99°F). In most cases, fever is a physiological response of the immune system to infection, inflammation, or other underlying medical conditions. While mild fever can be beneficial in fighting infections, a persistent or very high fever may indicate a serious illness that requires medical evaluation.

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Causes of Fever in Adults

Fever can result from a wide variety of conditions:

• Infections

  • Viral: Influenza, COVID-19, common cold, dengue, hepatitis

  • Bacterial: Pneumonia, urinary tract infections, tuberculosis, skin infections (cellulitis)

  • Parasitic: Malaria, toxoplasmosis

  • Fungal: Candidiasis, histoplasmosis

• Non-infectious inflammatory conditions

  • Autoimmune diseases (rheumatoid arthritis, lupus)

  • Inflammatory bowel disease

• Drug-related fever

  • Hypersensitivity to antibiotics, anticonvulsants, or other medications

• Cancer

  • Lymphomas, leukemias, and other malignancies can cause persistent low-grade fever

• Other causes

  • Heatstroke

  • Endocrine disorders (thyrotoxicosis)

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Symptoms Associated with Fever

• Elevated body temperature (≥ 38°C / 100.4°F)

• Chills and sweating

• Muscle aches and joint pain

• Fatigue and weakness

• Loss of appetite

• Headache

• Dehydration

• Irritability or confusion (especially in elderly patients)

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Red Flag Symptoms (Require Urgent Medical Attention)

Seek immediate medical help if fever is accompanied by:

• Temperature above 39.5°C (103°F)

• Persistent fever lasting longer than 3 days

• Severe headache with neck stiffness (possible meningitis)

• Shortness of breath or chest pain

• Severe abdominal pain

• Persistent vomiting or inability to hydrate

• Rash with purplish spots or bruising

• Seizures

• Altered mental status

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Treatment and Management

Treatment depends on the underlying cause. General management includes:

• Symptomatic treatment

  • Paracetamol (Acetaminophen): 500–1000 mg orally every 4–6 hours as needed (maximum 4 g/day).

  • Ibuprofen: 200–400 mg orally every 6–8 hours as needed (maximum 1200 mg/day for over-the-counter use).

  • Adequate hydration (oral fluids or IV fluids if severely dehydrated).

  • Rest and light clothing.

• Antibiotics

  • Only indicated if bacterial infection is confirmed or strongly suspected.

  • Examples: Amoxicillin 500 mg orally every 8 hours for bacterial respiratory infections (dose varies by infection type).

• Antiviral medications

  • Oseltamivir 75 mg orally twice daily for 5 days for influenza (if started within 48 hours of symptom onset).

• Antimalarials

  • Artemether-lumefantrine or chloroquine (depending on resistance patterns) for confirmed malaria.

• Corticosteroids or immunosuppressants

  • Used in autoimmune or inflammatory causes (prescribed by specialists).

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Self-Care and Home Management

• Drink plenty of fluids to prevent dehydration.

• Rest adequately.

• Avoid alcohol and smoking.

• Use a cool compress to reduce body temperature.

• Monitor fever with a reliable thermometer.

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Precautions

• Do not self-medicate with antibiotics without medical advice.

• Avoid aspirin in adults with viral infections due to risk of complications such as Reye’s syndrome (rare but serious).

• Elderly adults and immunocompromised individuals may have atypical fever responses and require careful monitoring.

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Drug Interactions

• Paracetamol: Increased risk of liver toxicity when combined with alcohol or other hepatotoxic drugs.

• Ibuprofen: May interact with anticoagulants (e.g., warfarin), antihypertensives, and corticosteroids (increased risk of gastrointestinal bleeding).

• Antibiotics: Can reduce effectiveness of oral contraceptives and interact with anticoagulants.

• Antivirals: May interact with warfarin, phenytoin, and methotrexate.