Q: My child has a high fever and I suspect the flu. When is the best time to get a flu test?

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 had a fever of 38.3°C around 8:00 AM this morning. By 10:30 AM, the temperature rose to 39.3°C, so I gave them a fever reducer. Given our surrounding circumstances, I highly suspect it might be the flu. When is the best time to visit the clinic for a flu test to ensure an accurate result? Last year, my child had to be tested twice because the first test came back negative right after the fever started.

Answer: It is completely understandable that you are concerned about the timing of the flu test, especially given your experience last year where testing too early resulted in a false negative.

Optimal Timing for a Flu Test

• The most accurate time to get tested for the flu is between 12 to 48 hours after the onset of symptoms.

• Since your child's first fever was recorded at 8:00 AM today, taking the test this evening or tomorrow morning would be the most appropriate timing.

• Testing too early (within the first 12 hours) significantly increases the risk of a false-negative result.

• Testing too late (after 48 hours) can also make it difficult to detect the virus because the viral load in the body begins to decrease.

Assessing the Current Situation

Given your child's high fever of 39.3°C, there is a strong possibility of the flu.

• A test taken after 3:00 PM to 4:00 PM today could potentially pick up the virus.

• Waiting until tomorrow morning will likely yield a more definitive and reliable result.

When to Seek Immediate Medical Attention

Please take your child to a doctor or emergency room immediately if they experience any of the following:

• Difficulty breathing or chest pain

• Decreased consciousness, extreme lethargy, or unresponsiveness

• Signs of severe dehydration

• A persistent fever of 40°C or higher that does not respond to fever-reducing medications

Starting antiviral medication (such as Tamiflu) within the first 48 hours is crucial for effectively treating the flu. Therefore, please make sure your child is evaluated by a pediatrician no later than tomorrow morning. Keep in mind that even if a rapid flu test comes back negative, a doctor can still prescribe antiviral medication if their clinical evaluation strongly points to the flu.

For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.

fevercoach.us

Apple App Store

Google Play

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