Q: If a fever rises to 38.4°C on the 3rd day of taking antibiotics, does it mean the medication isn't working?
Medically reviewed by Sang Hyun Ahn, MD
Content edited by Myeongchan Kim, MD
This post is a dramatization of a question and answer session experienced by our actual medical reviewers. Please note that this content is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
Question:
My child was prescribed antibiotics when they had a mild temperature around 37°C. Since starting the medication, they had a low-grade fever, but now on day three, the fever has spiked to 38.4°C (101.1°F) and the original symptoms haven't improved. Does this mean the antibiotic isn't working?
Answer:
It is understandable to feel anxious when a fever rises instead of improving while on antibiotics.
Assessing the Situation
Antibiotics typically begin to show clear clinical effects within 48 to 72 hours. While some infections may still involve intermittent fevers into the third day, a rising fever of 38.4°C along with no improvement in symptoms strongly suggests that the child needs an in-person medical re-evaluation. This could mean the antibiotic is not targeting the specific pathogen (such as in a viral infection or a resistant bacterial strain) or that the infection requires a different approach.
Signs You Should Contact Your Doctor Today
A fever that remains at or above 38°C (100.4°F) into the third day of treatment
Extreme low energy, refusal to drink fluids, or no wet diapers/urination for 8 hours or more
Rapid breathing, chest retractions (skin pulling in between the ribs), or pale/bluish lips
Any new symptoms appearing, such as an unexplained rash, persistent vomiting, or severe pain
What to Do at Home Right Now
Frequent hydration: Offer small sips of water, oral rehydration solutions, or clear liquids every 10 to 15 minutes.
Comfortable environment: Dress your child in light, breathable clothing and maintain a comfortable room temperature (around 22–24°C or 71–75°F).
Fever reducers: Use fever-reducing medications (acetaminophen or ibuprofen, if age-appropriate) primarily to relieve discomfort and improve hydration, focusing more on your child’s general condition than the exact number on the thermometer.
Do not stop the antibiotic arbitrarily: Continue the prescribed regimen until you have consulted your doctor, as stopping mid-treatment can worsen bacterial resistance.
When to Seek Immediate Emergency Care
Seek urgent emergency evaluation if your child shows any of the following red-flag signs:
Struggling to breathe, grunting, or turning blue around the lips
Becoming completely limp, unresponsive, or unable to make eye contact
Please reach out to the prescribing clinic or pediatrician today for a follow-up assessment so they can determine whether an alternate antibiotic or additional testing is needed.
For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.
