Medical tests save lives. But many Americans say they don’t have time to see a doctor, live too far from a medical facility or are so uncomfortable with examinations that they avoid tests altogether.

These challenges have created a demand for home-based medical tests. According to sales estimates, genetic health tests sold directly to consumers amounted to $99 million globally in 2017, with an annual average growth rate of 25.6 percent.

Most tests can be purchased online or at a pharmacy. A few require a doctor’s prescription, but all are administered by the patient at home. In addition to genetic tests, some detect or monitor existing conditions, like high blood sugar and cholesterol, colon cancer, sexually transmitted diseases and urinary tract infections.

Surprising discoveries

After learning that she was conceived with a sperm donor, Ann Melinger had “a lot of questions.”

When she heard about 23andMe, a genetics testing company that offers do-it-yourself kits, she thought it would be an easy way to learn more. 23andMe offers two kits that test a saliva sample to provide information about ancestry ($99) or both ancestry and some genetic health risks ($199).

Melinger’s test results revealed that she was positive for the BRCA1 mutation, indicating an increased risk for breast and ovarian cancer. She consulted medical specialists, including a genetic counselor to confirm the results and explain her risks.

Melinger, then 36 with two children, opted for the surgeries. “For me, it was really potentially lifesaving information.”

Home health tests are regulated by the FDA, which provides a database of approved tests on its website.

Many companies offer home-based genetics tests, and more are coming every day. CellMax Life offers two kits. One aims to identify 25 hereditary cancers by looking for mutations in 98 genes. Another tests not only for the BRCA1 and BRCA2 mutations, but also 13 other genes associated with the disease.

Prices vary, but most charge between $100 and $250 per series.

Some cautions

Megan Frone, a genetics counselor at the National Cancer Institute, said she thinks providing consumers with more tools for assessing their health can be beneficial.

Still, Frone urges consumers to do their homework before buying. Her advice: Look for a company with a Clinical Laboratory Improvement Amendment (CLIA) lab, a designation that signifies it meets federal quality standards. Find out whether your insurance will cover the costs. And ask whether the company shares your data with any third parties. Privacy “is a concern,” she said.

The tests’ accuracy and detail continue to improve, but for now, Frone tells users to take their results with a grain of salt. For one thing, scientists may not yet know the significance of a particular mutation. The concern, she said, is that consumers “walk away with just that small piece of information,” not knowing how it fits into the larger picture of their risks or what steps to take next.

Users should always follow up with a physician to confirm results.

Other home-based tests

Nina Mayo of Parma, Ohio, said home testing saved her life. When she refused to get a colonoscopy because of the preparation, her doctor offered an alternative: a test she could take at home called Cologuard. It tests for blood and any microscopic DNA fragments shed by a tumor or precancerous lesion. It requires a doctor’s prescription and costs $649, which some insurance plans cover.

Mayo said taking the test was easy. She mailed her sample and received the results two weeks later. They were positive. “I was horrified,” she said. “I completely, 100 percent expected a negative result.”

She was instructed to see a gastroenterologist who recommended a colonoscopy — the standard procedure following a positive result. It revealed two, large precancerous lesions, which the doctor removed. She said the doctor told her afterward: “You really dodged a bullet.”

Patients have many good options for screening. But “at the end of the day,” said Dr. Blase Polite, associate professor of medicine at the University of Chicago, “the best test is the one that you’re actually going to get.”