Quick Answer
A fever is generally considered dangerous when:
- • Adults: Temperature above 103°F (39.4°C) or persists more than 3 days
- • Infants (0-3 months): Any fever above 100.4°F (38°C)
- • Children: Temperature above 104°F (40°C) or accompanied by severe symptoms
🚨 Seek Emergency Care Immediately For:
Infants Under 3 Months
ANY fever of 100.4°F (38°C) or higher requires immediate evaluation. Infant immune systems are immature, and fever can indicate serious infection.
Fever + Severe Headache + Stiff Neck
This combination could indicate meningitis, especially if accompanied by sensitivity to light or confusion.
Difficulty Breathing
Fever with shortness of breath, chest pain, or rapid breathing may indicate pneumonia or other serious respiratory infection.
Altered Mental Status
Confusion, extreme drowsiness, difficulty waking, or hallucinations with fever require immediate attention.
Seizure
Fever-related seizures (febrile seizures) in children, especially if lasting more than 5 minutes or if it's the first occurrence.
Severe Abdominal Pain
Fever with intense stomach pain may indicate appendicitis or other surgical emergency.
New Rash That Doesn't Fade
Especially purple or blood-colored spots that don't blanch when pressed—could indicate sepsis.
⚠️ Call 911 or go to the emergency room immediately if you experience any of these symptoms with fever.
Fever Temperature Guidelines
Adults (18+)
- Low-grade: 99-100.9°F (37.2-38.3°C) - Usually manageable at home
- Moderate: 101-102.9°F (38.3-39.4°C) - Monitor closely
- High: 103-104°F (39.4-40°C) - Call doctor
- Very High: Above 104°F (40°C) - Seek medical care
Children (3 months - 17 years)
- Low-grade: 99-100.9°F (37.2-38.3°C) - Usually okay
- Moderate: 101-103.9°F (38.3-39.9°C) - Watch behavior
- High: 104°F+ (40°C+) - Contact doctor
- Emergency: 105°F+ (40.5°C+) or any concerning symptoms
📞 Call Your Doctor Within 24 Hours For:
- • Fever lasting more than 3 days in adults
- • Fever lasting more than 24 hours in children under 2 years
- • Temperature consistently above 102°F (38.9°C)
- • Fever that goes away and comes back
- • Persistent pain (ear, throat, urinary)
- • Fever in someone with weakened immune system or chronic illness
- • Fever after recent travel to tropical areas
- • Vomiting or diarrhea with fever lasting more than 24 hours
When Fever Is Protective
It's important to understand that fever itself is not an illness—it's your body's natural defense mechanism. Moderate fever actually helps your immune system fight infection by:
- • Slowing bacterial and viral reproduction
- • Enhancing white blood cell activity
- • Reducing iron availability to bacteria
- • Accelerating tissue repair
Home Care for Mild Fever
Stay Hydrated
Fever increases fluid loss. Drink water, clear broths, or electrolyte solutions. Avoid alcohol and caffeine.
Rest
Your body needs energy to fight infection. Avoid strenuous activity.
Dress Comfortably
Light clothing and keeping the room at comfortable temperature. Don't bundle up, as this can raise body temperature.
Medication (If Needed)
Acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) can help if fever causes discomfort. Follow dosing instructions carefully.
Important: Don't Give Aspirin to Children
Aspirin in children and teenagers with fever can cause Reye's syndrome, a rare but serious condition affecting the liver and brain.
Medical Review
Reviewed by: Ricardo Hamilton, MD
Last Updated: November 26, 2025
Sources: American Academy of Pediatrics, CDC Fever Guidelines, Mayo Clinic, Johns Hopkins Medicine