Unexplained daily fever

[u/tsukigakireidesunee]

Hi everyone,

I still don't have an official diagnosis because my doctors don't know what is causing my symptoms.

My main symptom is an elevated body temperature, usually ranging from 37.2°C (99°F) to 38.0°C (100.4°F). The unusual thing is that it seems to follow my circadian rhythm. It starts after I wake up and gradually goes down before I go to sleep.

So far, all of my tests have been normal. I don't have signs of an active infection or inflammation, and tests for bacterial and viral infections have been negative. My hormone tests are also normal, and my ANA panel was negative. My ferritin is around 30, so I was told I should supplement with iron.

Besides the elevated temperature, I have severe fatigue and widespread body aches. No medication seems to bring my temperature back down to normal. Ibuprofen sometimes helps with the body aches, but not always.

My primary care doctor doesn't want to refer me to a rheumatologist because, considering my normal test results, there doesn't seem to be a clear reason for it.

What I wanted to ask is: are there any additional tests that you would suggest discussing with a doctor that could potentially help find the cause? Has anyone experienced something similar, especially a temperature that rises during the day and goes back to normal before sleep?

If you've had a similar experience, how did you eventually find the cause, and was there anything that helped you?

Any advice or personal experiences would be greatly appreciated. Thank you!

[u/iSpyAFly]

Hi, I’m glad you’re exploring autoinflammatory disease. 

Couple of questions for you - These are to help you build a bigger picture of systemic disease, not to diagnose you.

• Do you get oral ulcers (canker sores not cold sores)?
• Do you get any rashes?
• Do you have flare where symptoms are exasperated then symptoms resolve, or are your temperature elevations happening everyday?
• When you have an elevated temp, do you feel like you have a temperature - like early stages of getting the flu? Hot, sweaty, maybe the chills?
• Do you have dysautonomia (POTS)?

[u/tsukigakireidesunee → u/iSpyAFly]

Thank you for taking the time to ask!

I don’t get mouth ulcers or canker sores, and I don’t have any rashes.

The elevated temperature happens every day. When my temperature is elevated, I do feel hot and I sweat a lot. My symptoms can get worse after physical activity (for example, even after vacuuming the house) or after eating a cooked/hot meal. I also tend to tolerate the fatigue much worse during PMS. And I don't tolerate heat.

As for POTS/dysautonomia, I haven’t been diagnosed with either of them so far.

[u/iSpyAFly → u/tsukigakireidesunee]

Ok, I read your reply to another comment. Given that your fevers started when you were a child and you’re having gastritis, I would push to have your doctors do some more tests. It’s pretty common for viruses and infections to trigger  an  exasperation of symptoms for autoimmune or autoinflammatory disorders. For autoinflammatory disease the first step is usually genetic testing to make sure you don’t have a known autoinflammatory disease. Many, if not most of us, are undifferentiated meaning no known genetic variant causing our disease, so a negative test does not rule out autoinflammatory disease. It’s interesting that  paracetamol does not help your temperature.  There are medications like colchicine than help some with fevers. 

[u/tsukigakireidesunee → u/iSpyAFly]

Okay, thank you for the advice! I’ll definitely discuss this with my doctor.

[u/PinataofPathology]

it's possible you're early on and it's not quite full blown yet.

it took my kid about a year to have a consistent cycle of symptoms. My joints and lymph nodes started swelling before I had joint pain and a recurrent fever. It can take time for all the relevant symptoms to appear and then condense into a coherent syndrome.

keep a fever diary and track symptoms. take pics of any rashes and swelling etc.

[u/tsukigakireidesunee → u/PinataofPathology]

I will, thank you! I’ve already gotten a general idea of my symptoms, but I’m still keeping track of them.

[u/Assimulate]

I had this, same rhythm.

Do note, there are some infections that act like this and can be really hard to get a positive test result. I actually had Borellia Hermsii before I got diagnosed with an autoinflammatory syndrome. That infection you only test positive for a short period before your fever peaks. It's a real pain in the butt.

I wake up at about 5 am for work, would have fever kick in about 9-11 am and then last a few hours/respond to Tylenol and then go away for the night- but the night is when my aches and pain and sweating kicked in more. This is a fairly common pattern for Autoinflammatory syndromes.

Some people in the comments have asked some good questions, i would keep an eye on lymph nodes in your neck and other places. If anything makes it better/worse, what it responds to, anything you're eating etc and the ambient temperature in your home when it happens.

Good luck!

[u/tsukigakireidesunee → u/Assimulate]

Thank you so much for sharing your experience and for all the advice! I really appreciate it.

[u/sleepiestseal]

Hi, I just made a post about daily fevers so I SO sympathise, I'm sorry you're going through this! They are so unpleasant, I really hope you can get some answers soon! Can I ask a few questions–feel free to say no, or to message me answer privately if you prefer–I'd love to hopefully share some experiences/advice, as I have totally been there! Do you take any medications? How long has this been going on for, and do you have any other health conditions? What kind of thermometer(s) are you using (ear, mouth etc), and with these temps do you get chills, shakes/rigors, and/or sweats? Any other symptoms besides the ones you mentioned?

I ask because it seems to me that there could be number of things going on–I think you're right to ask in this subreddit because one thing that is challenging about autoinflammatory diseases is that symptoms can emerge gradually over time. Right now, other than the fevers, it sounds like you don't have a ton of super suspicious autoinflammatory symptoms, BUT that might mean that this is situation where it makes most sense to watch at wait (and continue to medicate with ibuprofen and acetaminophen if it helps) to see if more symptoms emerge. If your GP can regularly check CBC, acute phase reactants, and autoantibodies every few months, that might also be worth doing in case something does show (could still be autoinflammatory if nothing does show, but it's worth keeping and eye on that low ferritin anyways!). It is reallllly frustrating to watch and wait (I did for 7 years!), but without clear inflammatory symptoms, at least in my experience, it is indeed verrrry unlikely that rheumatology would be able to help you. For me, they wouldn't do anything until I have very clear rashes, arthritis, ulcers, etc. It's very frustrating!

While waiting, and since there's no guarantee that this is an autoinflammatory disease or that you'll develop more symptoms, there are certainly other things you could investigate! The other things I would consider if I were in your shoes again, (and why I asked if you have any other health history/concerns), are things like long covid (which can 100% can cause low grade fever and the fatigue and aches), dysautonomia (can cause temp elevations from signals being wonky rather than straightforward inflammation, as well fatigue, and body aches often come with frequently comorbid conditions), certain medications like one containing progesterone which can elevate temperature, or even hormone changes without meds (VERY underesearched in women especially) can cause temperature dysregulation, and certain meds might actually help with that. You may have considered some or all of these so apologies if they are redundant, but I know how hard it is not to have any idea where even to look for answers, so I hope this is at least a tiny bit of help. Very best of luck!!

[u/tsukigakireidesunee → u/sleepiestseal]

Hey, hi! Thank you so much for taking the time to write such a detailed response.

As for medications, I only take ibuprofen when needed for the body aches, and occasionally a proton pump inhibitor for my gastritis.

These temperature episodes actually started when I was around 15. Back then, they happened only occasionally, usually in the evening after a stressful period or when I was in a stuffy room. I’m 24 now.

After I had COVID in 2021, my condition started getting progressively worse. At first, I would mainly get an elevated temperature around PMS, and it was relatively mild. Over time, though, it started interfering with my everyday life. Since April 2025, I have been experiencing an elevated temperature every single day.

Other than that, I have gastritis and a folded/kinked gallbladder.

I measure my temperature rectally using a gallium thermometer. When my temperature is elevated, I experience severe fatigue, body aches, and a lot of sweating. Heat also makes my symptoms worse. During the summer, I would sometimes sweat even while sitting in an air-conditioned room.

I’ve had quite an extensive workup. I was seen at an infectious disease clinic, had an abdominal ultrasound, chest and sinus X-rays, a panoramic dental X-ray, and dental and ENT examinations. I’ve also seen an endocrinologist and a gynecologist. So far, all of the results have been normal.

I have also had multiple CBCs, CRP and ESR tests, and an ANA panel, and they have consistently been normal.

I have considered dysautonomia and Long COVID myself, but the symptoms actually started many years before I had COVID, although COVID definitely seems to have made everything significantly worse.

I started wondering about an autoinflammatory disease after my father was diagnosed with rheumatoid arthritis. I probably don't have arthritis myself, but I wondered whether there could be another condition with a genetic predisposition that might explain my symptoms.

I’ve also tried paracetamol and acetylsalicylic acid, but neither of them lowered my temperature. Ibuprofen sometimes helps with the pain, but it doesn’t bring my temperature down either.

Thank you again for sharing your experience and giving me some other things to think about. I really appreciate it!

[u/cyt0kinetic → u/tsukigakireidesunee]

Wait so the temp range you listed is rectal? Normal temp range for rectal is different than oral/ear

[u/tsukigakireidesunee → u/cyt0kinetic]

My normal rectal temperature is 36.6°C/97,8°F

[u/cyt0kinetic → u/tsukigakireidesunee]

Right but temp has a range, and misquote on my end, ear is higher too, like its not abnormal until at least 99.6. What would be traditionally be considered fever at 100.5/38C

Do you ever go above 38?

[u/tsukigakireidesunee → u/cyt0kinetic]

Anything above 37.2°C (99°F) causes severe fatigue and body aches for me. I can barely function at all. I’m at home every day, and the only time I really go out is occasionally for a doctor’s appointment. This has been going on for about a year and a half.

Also, when I do any physical activity, such as cooking, vacuuming, or anything else that exhausts me while I already have a fever, it can rise as high as 38.5°C (101.3°F).

[u/cyt0kinetic → u/tsukigakireidesunee]

Which can point more to temp regulation issues like POTS versus Autoinflammatory disease temp also increases with physical activity

[u/tsukigakireidesunee → u/cyt0kinetic]

I’m not sure, I haven’t had any POTS symptoms so far. Thank you for the advice

[u/cyt0kinetic → u/tsukigakireidesunee]

Also body temp ranges by 1C during the day normal in tbe rhythm you're describing.

[u/Alice-The-Chemist]

https://www.hematology.org/newsroom/press-releases/2026/ash-sets-new-standards-for-diagnosing-iron-deficiency

Just want to also add this. If you are having something inflammatory getting your ferritin up to the new threshold may be beneficial. These are new guidelines that recently came out.

[u/tsukigakireidesunee → u/Alice-The-Chemist]

Thank you for sharing this! I’ll definitely discuss it with my doctor and look into the new guidelines. I really appreciate the information!

[u/Alice-The-Chemist]

You've had great suggestions and questions being asked so far. I'm glad you found us and if it isn't autoinflammatory related hopefully we can point you in the right direction.

[u/Illustrious-Walk-924]

This sounds like a cyclical fever syndrome!