"Why do I get nauseous at night?" Your immune system might be working in overdrive.

Here’s What It Means If You Feel Fine During The Day But Sick At Night

Hint: It probably has to do with your immune system.

by Julia Guerra and Amanda Arnold
Originally Published: 

We’ve all been there: You’re feeling pretty good during the day, having no issues getting through the workday and accomplishing your errands — and then, come nightfall, your body starts to feel like it’s falling apart. Maybe you can’t stop coughing, or you start to develop a low-grade fever. In short: You feel absolutely horrible, and you have no idea where all these symptoms suddenly came from. Why were you totally fine earlier and suddenly feeling nauseous at night? It’s worth doing a little digging to identify what’s triggering your nighttime discomfort. The root cause isn’t always an obvious issue, so you might have to think beyond your symptoms just a bit.

First of all, don’t panic — it’s actually extremely common to feel relatively OK during the daytime, only to feel absolutely dreadful at night. Still, it can be super frustrating when your conscious mind is like, “We’re all good here, so what gives?” and your body responds with a literal gut-wrenching stomach ache or vision-disrupting migraine right when you’re about to try to sleep. But almost nothing your anatomy does is by chance or accidental, and chances are, your body is trying to tell you something.

The most likely culprit is (surprisingly) your own immune system, which works especially hard at night to keep you healthy. But of course, there are a number of other factors that can contribute to why you might be feeling especially bad at night. To help understand the causes, Elite Daily spoke to Dr. Jared Braunstein, a primary care physician at the Medical Offices of Manhattan, who also advised on how to get your nighttime symptoms under control and when you should consider seeing a doctor.

Night Is When Your Immune System Works Overtime


There’s a reason why infections like the common cold, the flu, and stomach viruses tend to rear their ugly heads at night. During the daytime, when your body is busy expending energy moving around, digesting food, and whatnot, your immune system — which requires a lot of energy to power its activities — takes a backseat. Come nightfall, when the rest of your body is winding down, your immune system taps into that energy reserve and starts to rev up.

“Essentially, our immune system works on a circadian clock, in which most of the work is done while we sleep,” Braunstein tells Elite Daily. And when your system is fighting off viral or bacterial invaders, that immune response can “cause you to feel achy and feverish with sweats or possibly chills.” So, when your symptoms feel especially unbearable, just remind yourself that they’re proof you have a very strong immune system. Whatever pathogen you’re dealing with, hopefully your body is well-equipped to fight it off and feel better in the morning.

Lying Down Can Exacerbate Certain Illnesses And Symptoms

There are some illnesses and symptoms that tend to strike at night that have less to do with the time of the day, and more to do with what you tend to do come nightfall: lie down and go to bed. One such symptom is coughing.

“Coughs are worse at night because we tend to make more mucus at that time, and when we lie flat in bed, the mucus drips to the back of the throat and causes the cough reflex,” says Braunstein. Braunstein also highlights two other conditions that are exacerbated by lying down: acid reflux, “due to lying down too soon after a meal or having untreated acid reflux,” and — please don’t freak out or self-diagnose yourself — congestive heart failure, which can cause “shortness of breath while lying flat” if your heart isn’t adequately pumping to the lungs or rest of your body. This last scenario is unlikely, but if heart disease runs in your family, it might be worth checking in with your doctor to get their opinion.

You Could Just Be Noticing Your Symptoms More At Night

One other possibility is that you simply didn’t realize you were feeling sick until you took a moment to slow down. When you're so preoccupied with deadlines, meetings, class assignments, exams, or whatever else is on your to-do list, your mind doesn't have a chance to take a pause and process what’s happening in your body. This can be a good thing — a helpful thing, even, if you're able to organize and think rationally about the day you've had. But it can also distract you from noticing minor symptoms like a stomach ache, sinus pressure, or muscle soreness.

Make Sure To Drink Lots Of Water And Alleviate Your Pain Accordingly


The most important thing to do if you’re feeling ill at night — or at any time, really — is make sure you’re drinking lots of fluids. What else you should do depends on your symptoms. For example, if you have a really awful wet cough, you might try propping yourself up in bed with an extra pillow or two. Or, if you’re suffering from a fever or general achiness, Braunstein recommends taking an over-the-counter pain reliever, like Tylenol or Ibuprofen.

If Your Symptoms Don’t Alleviate After A Few Days, Seek Medical Attention

If you have one night with a burning fever or intense achiness, in all likelihood, you don’t have anything to worry about; just continue to hydrate and take Ibuprofen. However, “if pain or fever do not subside within three to four days,” Dr. Braunstein suggests reaching out to your doctor, as “you may have a bacterial infection, which would be best treated with antibiotics.” But again, try not to panic! Just do what you can in the meantime to get your symptoms under control, and see what your medical practitioner has to say.

Study referenced:

Haspel, J. A., Anafi, R., Brown, M. K., Cermakian, N., Depner, C., Desplats, P., Gelman, A. E., Haack, M., Jelic, S., Kim, B. S., Laposky, A. D., Lee, Y. C., Mongodin, E., Prather, A. A., Prendergast, B., Reardon, C., Shaw, A. C., Sengupta, S., Szentirmai, É., … Solt, L. A. (2020). Perfect timing: Circadian rhythms, sleep, and immunity — an NIH workshop summary. JCI Insight, 5(1).


Dr. Jared Braunstein, a primary care physician at the Medical Offices of Manhattan

This article was originally published on