Unexplained weight loss. Constipation. And periodically — yikes — a bit of blood in the toilet.

Were these signs that I had colon cancer?

The symptoms started earlier this year, a few months before my 50th birthday. Like so many of the worried well, I turned to the internet, and sure enough, several reputable sites seemed to indicate that I had reason for concern. Then I saw the news that colon cancer, though declining in older people, was on the rise in those aged 40 to 49.

I was about to turn that magic age when the medical guidelines call for colon-cancer screening, and as a result insurance companies pay for it. I figured that meant a colonoscopy — being put to sleep while a doctor snaked a long, black, camera-equipped tube into my colon — but there were other options.

This story has a happy ending. But along the way, I decided to look into the risks of self-diagnosis on the internet. Could too much information be a bad thing?

I have a science background, and I write about medical research for a living, so I should know better than to become rattled.

Start with the statistics. Yes, the rate of colon cancer has crept up since the mid-1990s for U.S. adults in their 20s, 30s, and 40s, according to an analysis published in February in the Journal of the National Cancer Institute — in each case, by 1 or 2 percent every year.

But these were increases in very small numbers. For those in their 40s, for example, the number of new colon cancer cases in a given year rose from 10 per 100,000 people in 1995 to about 13 per 100,000 in 2013. Not very common.

In May, I called my doctor's office, Abington General Internal Medicine, and described my symptoms to a nurse.

"Probably hemorrhoids," she said.

But the weight loss? I weighed 170 pounds during college. In the last few years, the scale has dipped below 165, to the point where my wife jokes that I look "scrawny."

Still a little wigged out, I called back a month later and spoke to my physician, Christina Kim.

"Probably hemorrhoids," she said.

Kim calmed me down a bit, evidently having picked up the art of a good bedside (or phone-side) manner at Temple University's medical school. She noted that colon cancer was uncommon, and that I had no family history of it. And my weight loss was not especially dramatic or sudden.

Physicians have long been accustomed to their patients consulting online symptom-checkers before picking up the phone, a phenomenon some refer to as "asking Dr. Google" or, in extreme cases, cyberchondria. One in three Americans has gone online to diagnose a medical condition, according to a 2013 survey by the Pew Research Center.

A brief word about sources: If you go online in search of health information, stick with quality. (U.S. Centers for Disease Control and Prevention, good. Gwyneth Paltrow's "Goop" site, bad.)

But even with good information, patients can lead themselves astray. In surveys, some doctors have said that these online quests can interfere with care, causing needless anxiety, and they lament any time they must spend on combating misinformation. Others say it is a good starting point for the doctor-patient interaction.

Kim, who has been at the Abington practice for five years, seemed fine with my online information-seeking. She said I could come in for an appointment to make sure that my medical issue was only hemorrhoids. But either way, the doctor said, by then I had turned 50 and was eligible for a colonoscopy, so it would not hurt to get one.

For colon cancer, there are noninvasive screening methods that may be just as good as colonoscopy, according to a 2016 recommendation by the U.S. Preventive Services Task Force, a volunteer panel of experts in preventive medicine. One is called the fecal immunochemical test (FIT), which detects blood in the stool. That is a possible sign of a tumor, at which point the physician would recommend following up with a colonoscopy anyway.

Physicians say the key is to choose a method and follow through, as early detection of colon cancer markedly improves the odds of survival. Yet one-third of eligible U.S. adults have never been screened, according to the task force.

Concerned that the FIT test might not distinguish between the blood from hemorrhoids and that from a possible tumor, I decided to go straight to the colonoscopy. It would be more expensive, but if the doctor did not find anything, I could wait 10 years before doing it again — whereas the FIT test must be done annually. What's more, if the colonoscopy did "find something" — an abnormal protrusion called a polyp — the doctor could remove it then and there.

My insurance carrier at work changed, and a few more months went by before I got my act together. I finally got an appointment for a colonoscopy on Sept. 12 at Holy Redeemer's Ambulatory Surgery Center in Huntingdon Valley.

People say the worst part is the prep — the noxious liquid that must be drunk in advance to, ahem, clean out your system — and they are right. That, and the fact that you cannot eat anything for more than a day, other than clear liquids, such as chicken broth, the night before the procedure.

At 6 p.m. the night before the procedure, I drank my first dose of the prep liquid, which tasted like salty cough syrup. I followed that with two glasses of water, and settled in for an evening of visiting the bathroom. The next morning at 7 a.m., I repeated the process.

The actual colonoscopy was no big deal. My wife drove me to Redeemer's outpatient surgery center at noon so I could fill out paperwork and put on a hospital gown. Gastroenterologist Martin Chatzinoff, who performs about 1,000 colonoscopies a year, told me that polyps are found in 20 percent to 30 percent of patients. But most of those do not turn out to be cancerous.

Shortly after 1 p.m. the anesthesiologist put me under, and 30 minutes later, it was all over.

"No polyps," said Chatzinoff, whose practice, Gastrointestinal Associates, is in Rydal. "Come back in 10 years."

The blood was indeed from hemorrhoids. And the constipation? Not enough water, maybe.

Now I just need to steer clear of alarming information on the internet. Fat chance.