Persistent Low-Grade Fever: Causes and Next Steps

Recently, there has been an elevated body temperature for the past month?

Hello Doctor: I discovered that I had recurrent low-grade fevers at the end of October, and subsequently visited a large hospital for evaluation.
Blood and urine tests revealed a urinary tract infection.
I underwent antibiotic treatment for two weeks.
The week before treatment, I had a fever reaching 38.5 degrees Celsius, but after one week, I did not experience any low-grade fever.
However, two days after completing the medication course, I started having low-grade fevers again.
This morning, my temperature was around 36.8 to 37.3 degrees Celsius, and after noon, it ranged from 37.4 to 37.7 degrees Celsius, accompanied by dizziness.
I was wearing only a short-sleeve shirt and a down jacket, and upon arriving at the hospital, my temperature was measured at 37.9 degrees Celsius.
Why does low-grade fever typically occur in the afternoon? Today, I visited the infectious disease department at the large hospital, where only blood tests were conducted.
The doctor mentioned that my white blood cell count was within normal limits, and there were no signs of inflammation in my liver or kidneys.
I asked the doctor why there were no signs of inflammation in the blood tests, yet I still experience low-grade fevers.
Are there any other potential causes for this? Are there more advanced tests that can be performed? Additionally, after taking a hot shower at home in the evening, my temperature tends to decrease after half an hour to an hour.

Mr. Hong, 30~39 year old female. Ask Date: 2021/11/22

Dr. Ye Qianyu reply Family Medicine

Hello! Body temperature can also be influenced by the environment, clothing, and diet.
Some viral infections may not show changes in blood tests.
Please avoid spicy or warming foods and supplements that may increase body temperature or promote blood circulation.
Additionally, be aware of any other accompanying symptoms.
If you experience palpitations, tremors, or weight loss, please consult a metabolic specialist.
If you have gastrointestinal discomfort, nausea, or loss of appetite, please see a gastroenterologist.

Reply Date: 2021/11/22

More Info

Persistent low-grade fever can be a perplexing symptom, especially when it recurs after treatment for a previously diagnosed condition, such as a urinary tract infection (UTI). In your case, it appears that after a course of antibiotics, the fever returned, which raises several considerations regarding potential underlying causes and the next steps for evaluation.

Firstly, it is important to understand that low-grade fever, typically defined as a body temperature between 99°F (37.2°C) and 100.4°F (38°C), can be influenced by various factors, including infections, inflammatory conditions, and even environmental factors. In your situation, the initial diagnosis of a UTI was appropriate given the symptoms and subsequent fever. However, the recurrence of fever after antibiotic treatment suggests that there may be other factors at play.

One possibility is that the initial infection was not fully resolved, or there may be a new or different infection that has developed. It is also worth noting that some infections, particularly viral infections, may not always show significant changes in blood tests, including white blood cell counts or inflammatory markers. Therefore, even if your blood tests returned normal results, it does not entirely rule out an infectious process.

Other potential causes of persistent low-grade fever include:
1. Chronic Infections: Conditions such as tuberculosis, endocarditis, or abscesses can lead to prolonged fever without clear initial symptoms.

2. Autoimmune Disorders: Conditions like lupus or rheumatoid arthritis can cause fever as part of their symptomatology.

3. Malignancies: Certain cancers can present with fever as a paraneoplastic syndrome, even in the absence of other symptoms.

4. Environmental Factors: As you mentioned, your fever tends to occur in the afternoon. This could be related to circadian rhythms, where body temperature naturally fluctuates throughout the day. Additionally, factors such as dehydration, fatigue, or stress can contribute to feelings of malaise and low-grade fever.

5. Hormonal Changes: In women, hormonal fluctuations during the menstrual cycle, particularly during ovulation, can lead to slight increases in body temperature.

Given the complexity of your symptoms, further evaluation is warranted. Here are some recommendations for next steps:
- Follow-Up with a Specialist: Since you have already seen an infectious disease specialist, consider returning for further evaluation. They may recommend additional tests, such as imaging studies (e.g., ultrasound or CT scan) to rule out abscesses or other hidden infections.

- Comprehensive Blood Tests: A more detailed blood panel, including tests for autoimmune markers, cultures, and possibly a complete metabolic panel, could provide more insights.

- Consider a Referral to a Rheumatologist: If autoimmune conditions are suspected, a rheumatologist can perform specific tests to evaluate for these disorders.

- Monitor Symptoms: Keep a detailed log of your symptoms, including temperature readings, associated symptoms (like dizziness or fatigue), and any potential triggers (such as stress or dietary changes). This information can be invaluable for your healthcare provider.

- Lifestyle Adjustments: Ensure you are maintaining a balanced diet, staying hydrated, and managing stress, as these factors can influence your overall health and potentially your symptoms.

In conclusion, while persistent low-grade fever can be frustrating, it is essential to approach it systematically. By working closely with your healthcare providers and considering a broad differential diagnosis, you can identify the underlying cause and receive appropriate treatment.

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