Colon cancer kills about 50,000 Americans per year. (iStock)

Colon cancer kills about 50,000 Americans per year. And screening does save lives. But getting a colonoscopy isn’t risk-free. About three out of every 1,000 people who have the procedure experience serious complications, such as bleeding and perforation. The chances of having a problem depend in part on where the procedure is done and the kind of anesthesia used.

Here’s what you need to know.

When you need screening. Experts say that most people should have their first colonoscopy at age 50. If no precancerous polyps or cancer are found, you can usually wait a decade for the next one. But many doctors tell even low-risk patients to come back sooner.

Guidelines also say that most people can stop screening at age 75, when the risks of the test begin to outweigh its benefits. But a 2013 study found that about two-thirds of those over that age may have had unnecessary colonoscopies. So if your doctor says that you need a colonoscopy more than once a decade or after 75, ask why.

Instead of colonoscopy. There are screening options less invasive than colonoscopy, including a DNA test called Cologuard, which was approved by the Food and Drug Administration last summer. It requires taking a stool sample at home and sending it to a lab for analysis, and it may need to be repeated every three years.

Options with proven track records include an annual test for blood in the stool, and sigmoidoscopy (which examines only the lower third of your colon) every five years plus a stool test every three years. If the results of any of those tests are worrisome, you’ll need a colonoscopy to confirm the results.

Find out about anesthesia. Many people think they need to be fully knocked out during the procedure. But it can be done without anesthesia or with conscious sedation, which uses a drug such as midazolam to ease pain while allowing you to be alert. “You should aim for the lightest level of sedation you need,” says Orly Avitzur, Consumer Reports’ medical adviser. “The trend toward deep sedation is worrisome because it increases risk.”

Find the right clinic. Most colonoscopies are done not in hospitals but in ambulatory surgery centers. That’s okay; research suggests that they’re as safe as hospitals for the procedure.

But not all centers are equal. Look for one that is Medicare-certified, and ask how many of the clinic’s colonoscopy patients have had to be hospitalized because of infections. “The right answer is zero,” says Lisa McGiffert of Consumer Reports’ Safe Patient Project.

Going to a hospital for a colonoscopy can be safer if you have had a recent heart attack or you have lung disease or another risk factor.

Check your bill. The Affordable Care Act requires insurers to cover screening colonoscopy. But ask your insurer whether you’ll have to pay for a prep kit or for part of the pathology, facility and anesthesiology fees. Check your bill afterward as well. Diagnostic colonoscopies, used to investigate symptoms such as stomach problems or anemia, don’t have to be fully covered, so doctors might code your procedure to fall into that category, leaving you with a big tab.

The best way to prep. You’re limited to a clear-liquid diet for about 24 hours before the procedure, and you might have to drink up to a gallon of a laxative solution. To improve the taste, chill it first or ask your doctor whether it’s okay to add lemon, lime, ginger or a flavor enhancer such as Crystal Light. Other steps that might help include eating more lightly than usual, including less fiber, for a few days before your exam, using a straw to drink the solution, staying near a bathroom and using flushable wipes and diaper ointment to soothe irritation.

Copyright 2015. Consumers Union of United States Inc.

For further guidance, go to www.ConsumerReports.org/Health, where more detailed information, including CR’s ratings of prescription drugs, treatments, hospitals and healthy-living products, is available to subscribers.