Q: How long does a flu fever last? I got a Peramiflu injection yesterday, but my fever is still 38.7°C with a severe sore throat.
- Myeongchan Kim, MD
- Jul 9
- 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:
I started having flu symptoms on Sunday evening and received a Peramiflu injection on Monday morning. However, my fever is still persisting. It's around 38.7°C. I don't feel the need to alternate fever reducers, but my throat hurts severely. Is the fever persisting because my throat is swollen? How long will this flu fever last?
Answer:
I understand your concern about the persisting fever even after receiving the Peramiflu treatment on Monday morning.
Understanding Your Current Symptoms:
Fever Duration: It is very common for a fever to continue for 24 to 48 hours after receiving an antiviral flu medication like Peramiflu.
Fever Management: Since your temperature is around 38.7°C and you are managing it without needing to alternate different fever reducers, it is highly likely that the medication is actively working in your system.
Sore Throat: The severe throat pain and swelling you are experiencing can be caused by the flu virus itself or an accompanying condition like pharyngitis.
Home Care Recommendations:
Hydration: Take frequent, small sips of water or thin gruel. This keeps your throat moist and prevents dehydration.
Environment: Wear light, breathable clothing and keep your room at a comfortably cool temperature.
Medication: If you are uncomfortable, take a single type of fever reducer (such as Acetaminophen or Ibuprofen) following the standard dosage instructions on the label.
Soothing the Throat: Warm drinks or honey tea (only appropriate if the patient is over 1 year old) can help soothe the throat.
When to Seek Immediate Medical Care:
Please visit a doctor right away if you experience any of the following warning signs:
Difficulty breathing or a feeling of tightness in the chest.
No urination for more than 8 hours.
Fever that does not start to drop after 48 hours, or spikes higher.
Throat pain so severe that you cannot swallow your own saliva, or a sudden change in your voice.
Severe lethargy, sluggishness, or unusually slow responses.
For now, I recommend calling the clinic that prescribed the Peramiflu. Let them know that it has been 24 hours since the treatment, but your fever and severe sore throat are persisting. They can advise if an in-person throat re-examination or additional treatments are necessary. Focus on getting plenty of rest and fluids today, and please seek an immediate in-person medical evaluation if any of the warning signs mentioned above develop.
For extra peace of mind and clear guidance when tracking your child's symptoms, the FeverCoach app is always there to help.
