Q: My 7-year-old had a negative flu test on day 1 but still has a high fever on day 3. Should we get a retest?
- Myeongchan Kim
- May 25
- 2 min read
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 7-year-old child started having a mild fever on Saturday evening. By Sunday lunchtime, the fever spiked to 38.8°C. I gave them a fever reducer, and the temperature dropped to 37.1°C. We visited the clinic at 3 PM on Sunday, and a rapid flu test came back negative. The doctor noted that my child's tonsils and nasal passages were swollen.
Now it is the third day, and the fever keeps spiking up to 39°C. When I give a fever reducer, the temperature only drops to 37.8°C and then rises again five hours later. Should we do another flu test? I am asking because I heard that if a flu test is done less than 24 hours after a fever starts, it might show a false negative.
Answer:
I understand your concern regarding your 7-year-old child's persistent high fever. Based on the symptom pattern you described, it is highly advisable to consider retesting for the flu.
Here are the reasons why a retest is recommended:
• The initial test may have been performed too early. Testing within the first 24 hours of symptom onset often results in a false negative.
• A high fever of 39°C is persisting into the third day, and the effect of fever-reducing medications is limited.
• Swollen tonsils and nasal mucosa are very common clinical signs of the flu.
Regarding the timing for the retest:
Going in tomorrow morning would be ideal, as more than 72 hours will have passed since the symptoms started, making the test much more accurate. Testing this evening is also an option, but waiting until the morning may yield a more definitive result.
Please seek immediate medical attention or visit an emergency room if your child experiences any of the following "red flag" symptoms:
• Difficulty breathing or chest pain
• Decreased consciousness, extreme lethargy, or unresponsiveness
• Signs of severe dehydration (not urinating, no tears when crying)
• A fever that remains above 40°C despite taking fever reducers
For home care in the meantime:
• Encourage frequent fluid intake (warm water or electrolyte drinks) to prevent dehydration.
• You can cross-alternate different classes of fever reducers (e.g., Acetaminophen and Ibuprofen) with a 3-hour interval if a single medication is not keeping the fever down.
• Use a humidifier to keep the respiratory passages moist and ensure your child gets plenty of rest.
If the flu is confirmed upon retesting, antiviral medications (such as Tamiflu) can be prescribed. Early treatment is important for a quicker recovery, so please visit your pediatrician for a re-evaluation and follow their clinical guidance.
For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.
