Unexplained Nighttime Fever: Causes and When to Seek Help

Fever of unknown origin at night?

Hello, Doctor.
On July 28th, around 8 PM, I started feeling warmth in my cheeks and experiencing a rapid heartbeat.
Even in an air-conditioned room, I was sweating continuously.
Later, when I lay down to sleep, I felt my heart racing and continued to sweat with warmth in my cheeks.
On the morning of July 29th, I woke up with my face covered in sweat and my cheeks flushed.
The clinic's ear temperature readings were 37.1°C and 37°C, which don't seem to indicate a fever.
After taking antipyretics, I did not experience any fever throughout the day on July 29th (I took one packet of antipyretics in the morning and another at noon).
However, around 8 PM (after dinner), I began to feel warmth in my cheeks, a rapid heartbeat, and sweating again.
What could be the issue? I have not experienced any cold symptoms so far.
My menstrual cycle is expected around the 5th to 6th of the month; could this be related to premenstrual syndrome? Should I get a blood test? If so, what tests would you recommend? Thank you, Doctor.

Peggy, 30~39 year old female. Ask Date: 2018/07/29

Dr. Hong Yuanbin reply Internal Medicine

Hello, based on the temperature you measured, there is indeed no fever present.
As for the feeling of having a fever that you described, there are many possible causes, including premenstrual syndrome and endocrine issues.
I recommend that you first visit an infectious disease specialist or a family medicine clinic to check your white blood cell count and inflammatory markers, as this will help in making further assessments.
Thank you for your inquiry.

Reply Date: 2018/07/29

More Info

Unexplained nighttime fever can be a perplexing symptom that may arise from various underlying causes. Based on your description, it seems that you are experiencing episodes of facial flushing, increased heart rate, and sweating, particularly in the evening, without any apparent fever during the day. This pattern can be indicative of several conditions, and it is essential to consider both physiological and psychological factors.

One possibility is that you are experiencing symptoms related to hormonal fluctuations, especially if your menstrual cycle is approaching. Premenstrual syndrome (PMS) can manifest with a variety of symptoms, including mood swings, anxiety, and physical symptoms such as bloating and changes in body temperature regulation. Hormonal changes can also affect the autonomic nervous system, leading to symptoms like increased heart rate and sweating. If your symptoms align with your menstrual cycle, it could indeed be related to PMS.

Another consideration is the possibility of anxiety or stress-related responses. The body can react to stressors by activating the sympathetic nervous system, which can lead to symptoms such as palpitations, sweating, and a feeling of warmth. If you have been under increased stress or anxiety, this could explain the symptoms you are experiencing at night.

Infections, although less likely given your lack of other symptoms, should not be ruled out entirely. Some infections can present with atypical symptoms, and it is possible to have a low-grade infection that does not manifest as a full-blown fever during the day. If you experience any additional symptoms such as fatigue, body aches, or gastrointestinal issues, it would be prudent to seek medical attention.

Given your situation, it would be advisable to monitor your symptoms closely. Keeping a diary of your symptoms, including the timing, duration, and any accompanying factors (such as stress levels, dietary changes, or sleep patterns), can provide valuable information for your healthcare provider. If your symptoms persist or worsen, it would be wise to consult with a healthcare professional.

In terms of laboratory tests, if you decide to seek medical attention, your doctor may recommend a complete blood count (CBC) to check for signs of infection or inflammation. Additionally, tests for thyroid function, hormone levels, and possibly inflammatory markers could be considered, especially if there is a suspicion of an underlying endocrine disorder.

In conclusion, unexplained nighttime fever and associated symptoms can arise from a variety of causes, including hormonal changes, stress responses, or infections. Keeping track of your symptoms and consulting with a healthcare provider will help in determining the underlying cause and appropriate management. If your symptoms are impacting your quality of life or causing significant concern, do not hesitate to seek medical advice sooner rather than later.

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