It's that time of year again. You wake up with a scratchy throat, stuffy nose, a little achy — maybe a fever. Is it a classic head cold, or do you need to be more concerned? Could it be the flu?

"There's lots of confusion out there, because both are viral respiratory illnesses," says Dr. Yul Ejnes, an internal medicine specialist in private practice in Rhode Island and spokesperson for the American College of Physicians. "No one likes to get a cold, but people are more fearful of the flu."

And rightly so.

Last year's influenza season was particularly severe, resulting in an unusually high number of hospitalizations and deaths from flu complications.

So, if you do have the flu, it's important to consult with your health care provider about treatment. And distinguishing between a cold and flu may be easier than you think, Ejnes says. There are some clear distinctions between the two similar types of viral illness in terms of symptoms — how quickly they appear and how severe they become.

Suddenly flattened? Think flu

Flu symptoms, Ejnes says, usually start abruptly — though you can spread the virus before symptoms surface.

"Patients can pretty much tell you when the symptoms hit them — after lunch, for example, or yesterday afternoon," says Ejnes.

A cold, on the other hand, takes a couple of days to build up. You may have a scratchy throat one day and then the nose starts to get stuffy the next day.

You may also develop a fever with a cold. But typically, it's a "low-grade" rise in temperature, hovering around 99 or 100 degrees Farenheit.

With flu, that fever is usually significantly higher — at least 101 degrees. Chills and body aches are another flu hallmark or, as Ejnes says, "feeling like a truck ran you over — where you can't even move a muscle."

Dragging yourself out of bed can seem impossible when you have the flu. "You're just wiped out with total body fatigue," he says, whereas with a cold, people often "soldier on" and get out of bed for work or social activities.

Heading to work isn't a good idea, of course, even with a mild cold, because it exposes others to the virus -- but lots of people do it. (Colds tend to be most contagious in the first several days of illness.)

There can be congestion and cough from the postnasal drip of a head cold, but it's not nearly as severe as with flu. Influenza can trigger long bouts of coughing and even trouble breathing.

So, when patients tell Ejnes that their symptoms developed suddenly, their fever is high and their body aches severe, he assumes flu, he says.

But should those symptoms send you to the doctor? That depends, Ejnes says. If you're a healthy adult without any chronic health problems, you may instead do fine with merely phoning your doctor, who can quickly prescribe any of several antiviral medications. That medicine is most effective when given within two days of symptoms.

"It's not a miracle drug by any stretch," cautions Ejnes, but it can offer some relief by reducing the severity of symptoms and the duration of the illness by a day or so.

Ejnes says he prefers a phone chat to a visit in such cases — partly to limit the number of people in his waiting room who have the flu.

"I've had the most ironic scenarios, where somebody's coming into the office to get a flu shot and — while they're waiting to be called in — they're sitting next to someone who's coming in with symptoms that might be the flu."