When I came down with a hacking cough a few weeks ago, I wasn't too concerned — I assumed that I had simply caught a cold, the same cold that every human being in town seemed to be nursing at the time. But as the days passed, I noticed that my cold seemed different than the ones I'd had in the past — my nose barely ran, but I had a hideous dry cough that woke me up in the middle of the night. I also wasn't getting any better; if anything, I seemed to be getting worse. But I was convinced that it was just a cold, because ... well, because it wasn't the flu, and those are pretty much your only two options, right?

After a week, I finally began to wonder if my cold had lasted long enough to see a doctor about it, and booked an appointment with my GP. I assumed he would pat me on the back, be mildly annoyed that I had wasted his time, and send me on my way; instead, he told me I had an acute upper respiratory infection — basically a cold that had gotten way out of hand. He sent me home with prescriptions for prednisone and some very strong, Trainspotting-level cough syrup. I took the medicines, finally slept through the night, and felt way better in less than a day.

How can you learn from my cough-related foolishness? Don't assume that literally any sickness that gives you a cough or runny nose is just a cold. There are a number of more severe illnesses with similar symptoms — so pay attention.

For more tips on how to tell the difference between your standard "sit on the couch, watch Bojack and pity yourself" cold and something more serious, as well as some info on how long a cold should last before you see a doctor, read on.

1. Your Cold Got Worse

You seemed to have started off with a regular, garden variety cold — but suddenly, things are so bad that you can't work, you can't sleep properly, and you're not getting any better. Basically, you feel like a bagel that got dropped into a filthy sidewalk puddle. What on earth is going on with your danged body?

"If you start to feel worse and really aren't feeling better after three to four days," Dr. Dana Hawkinson, MD, an infectious diseases expert and assistant professor at the University of Kansas Medical Center, tells Bustle, "that can be a sign that [the illness is] maybe going down to your lower respiratory tract, to your lungs, which could cause things like pneumonia, which is an infection in the lungs."

You may have developed what's known as a secondary infection. A secondary infection can occur when your immune system is weakened by a primary infection — say, you contract the cold virus, and then contract a bacterial pneumonia as your secondary infection. Common secondary infections can include sinusitis, bronchitis, and pneumonia — serious illnesses that either require or can really benefit from medical attention.

2. Your Cold Has Lasted More Than Two Weeks

Most colds last one week to 10 days, according to the Mayo Clinic. People who are lucky may only have a cold for three days; people who are really unlucky might be sick for two weeks. But if you cold has lasted for more than two weeks — and especially if it doesn't appear to be getting any better — let someone in a lab coat look at you.

"Unless you've had symptoms for two weeks or more, it is probably viral," like a cold, says Hawkinson. But if your illness is lasting longer, see a medical professional, who can see if your illness is actually bacterial.

3. Your Eyes Are Watery Or Itchy

If your "colds" happen at roughly the same time every year, you might not be catching a viral illness at all — you may instead have seasonal allergies. It's difficult to tell the difference between a cold and allergies sometimes, since they share so many symptoms, like sneezing and having a runny nose. Hawkinson suggests keeping an eye out for fevers (never a seasonal allergy symptom); also, note if you have itchy eyes (rarely a cold symptom),

4. You Suddenly Became Incredibly Ill

Colds usually have a bit of a build up. But a flu can take you from "zero" to "I am an extra on The Walking Dead" over the course of a day.

The flu "hits you like a bolt of lightning," Steven Lamm, MD, internist and faculty member at NYU School of Medicine, tells Prevention. "You’ll likely run a fever of above 101F, and you'll be flat out." So if you suddenly feel too sick to function, know that you probably have a flu on your hands — and it's good to know sooner rather than later, because most antiviral treatments for flu work best when taken within 48 hours of the onset of symptoms.

5. You're Mostly Coughing

We're conditioned to believe that anything that involves coughing or sneezing is just a cold. But an illness whose primary symptoms are coughing, wheezing, and pain or tightness in your chest could be bronchitis — and since, according to the Mayo Clinic, bronchitis commonly occurs in people who have just had colds, you might not even notice that you've developed it.

Though some cases of bronchitis clear up on their own, others may require medication — so make sure to see a doctor to find out what you're dealing with.

6. You Suddenly Develop A Fever

If you didn't start out with a fever, but develop one several days after the start of your illness, that could be a sign that something more complex is afoot. "If your symptoms worsen, such as worsening actual fever or new symptoms [like] progressive worsening headache or progressive worsening cough and chest pain," you could be developing a secondary infection, says Hawkinson.

7. It Hurts To Swallow

Strep throat can often feel like a run of the mill cold-related sore throat at first. But if you have strep throat, your symptoms will feel different — according to the CDC, strep throat sufferers may experience pain swallowing, fever, swollen lymph nodes, and swollen tonsils.

It's important to get your strep throat treated — letting it linger can lead to serious illnesses like rheumatic fever or even inflamed kidneys. So if you think your sore throat could be strep, head straight to the doctor — they can give you an easy test to figure out if you do indeed have strep, and if you do, they can give you the proper medications to help you feel better.

How Long Should A Cold Last Before You Go To The Doctor?

And how can you tell when it's time to seek medical attention? "It just kind of boils down to knowing your own body, knowing what type of symptoms you're feeling," Hawkinson says. "Are you really beginning to feel better or are you actually feeling worse? And that is probably the best guideline to go by."

This post was originally published on November 6, 2015. It was updated on July 1, 2019.