Q: My child's fever is rising to 38°C. When is the best time to get a flu test?
- Myeongchan Kim, MD
- Jul 12
- 2 min read
Updated: Jul 21
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:
Hello, yesterday my child had a mild fever of 37.5-37.6°C. It didn't go any higher, and their temperature was normal during the night. However, today around 10 AM, it went up to 37.6°C, and two hours later, it hit 38°C. It seems to be steadily rising. Would it be better to get a flu test tomorrow? Will the result be accurate if we do it today?
Answer:
Hello! It is completely understandable that you are worried as the fever continues to rise. Here is some guidance regarding the best time to get a flu test:
[Optimal Timing for a Flu Test]
• The test is most accurate when performed 12 to 24 hours after the onset of symptoms.
• Since the mild fever started yesterday, late this afternoon or tomorrow morning would be an appropriate time to test.
• Testing too early can sometimes result in a false negative.
[Evaluating the Current Situation]
Given that the fever is currently rising to 38°C:
→ You could get tested late this afternoon (which would be around 24 hours after the initial symptoms began).
→ However, getting tested tomorrow morning might yield an even more accurate result.
[Things to Discuss During Your Doctor's Visit]
When you visit the clinic, it is helpful to inform the doctor about:
• Any accompanying symptoms such as muscle aches, headaches, or a cough.
• Any recent exposure to someone diagnosed with the flu.
• Whether the child has received this season's flu vaccine.
Please note that if your child is struggling severely, experiencing difficulty breathing, or showing signs of dehydration, you should seek immediate medical attention regardless of the ideal timing for a flu test.
Since the fever is currently rising, please ensure your child stays well-hydrated and use fever reducers (antipyretics) to keep them comfortable until they can be evaluated by a pediatrician.
For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.
