The last time you went to the gynecologist, which tests did you get?

One in nine American women miss out on key tests that spot cervical cancer in its earliest, most treatable stages, says a new report. More than 8 million American women haven’t had a Pap test, which looks for suspicious cell changes on a woman’s cervix, or an HPV test, which looks for the virus that causes cervical cancer, in the past five years according to the Centers for Disease Control and Prevention (CDC).

More than half of all cervical cancers happen in women who don’t get these checks often enough. Every year, more than 12,000 U.S. women find out they have invasive cervical cancer. This cancer kills 4,020 women annually, according to the American Cancer Society. But it doesn’t have to. The Pap and HPV tests find early warning signs that let doctors stop cervical cancer, often before it starts.

If you feel confused about if and when to get these tests, you’re not alone. Recent, reports from major health groups are changing the rules about who needs them and who doesn’t. Here’s what women need to know.

Keep up with annual pelvic exams.This stirrups-and-speculum check of your reproductive organs is the time when your doc will do a Pap and/or HPV test if you need them. The American College of Obstetrics and Gynecology recommends pelvic exams annually for most women, despite a recent report from another group (the American College of Physicians) questioning the value of the annual exam. If you’re unsure about what to do, talk it over with your gynecologist. If you decide not to have the pelvic exam annually, be sure to go often enough to get the cervical cancer checks you need.

Follow this Pap and HPV test schedule. For both tests, your healthcare provider will use a tiny brush or other tool to painlessly take cell samples from the surface of your cervix during your pelvic exam. The cells are sent to a lab for testing. The American Cancer Society and the U.S. Preventive Services Task Force recommend this schedule:

For women 21 to 65: Have a Pap test every three years. Or, if you’re between 30 and 65, have a Pap test plus an HPV test every five years.

For women younger than 21: Skip cervical cancer tests. Women younger than 21 are at low risk for cervical cancer and most cell changes found with a Pap test go away on their own, says the National Cancer Institute.

For women over 65: Skip cervical cancer tests if you’ve been tested regularly in the past and are not at high risk for cervical cancer. Talk with your doctor about testing based on your personal history.

For women who have had their cervix removed during a hysterectomy: Skip cervical cancer tests if you do not have a previous history of cervical cancer or precancerous changes. Talk with your doctor.

For women who’ve had cervical cancer or a precancer in the past: Talk with your doctor about future screenings. After treatment, you may need more frequent checks.

If you’ve gotten the HPV vaccine, have the screenings recommended above. Yes, the vaccine protects you from the strains of human papilloma virus most likely to cause cervical cancer. But it’s not perfect. You still need cancer checks because the vaccine doesn’t cover all HPV strains that can cause cancer.

If your Pap test results are “unclear” or abnormal or if your HPV test is positive, here’s what to expect. You’ll likely need additional checks such as a repeat Pap test, an HPV test or a more in-depth exam of your cervix called a colposcopy. Your doctor may also collect cell samples for testing. If tests spot precancerous changes or cancer, your doctor will discuss treatments that can stop this cancer. But take a deep breath. Of the 3 million American women whose Pap results are “unclear” each year, about 10,000 may have cancer according to the CDC.

If your HPV test is “negative,” it means you don’t have an HPV strain that causes cervical cancer. If it’s “positive,” you have a strain that can cause cancer. Your doctor will look at your Pap results to see if you have cell changes that could be precancerous or cancer and make decisions about treating the cells or waiting and rechecking.

Sari Harrar is an award-winning health, medicine and science journalist whose work appears in Dr. Oz The Good Life magazine, Good Housekeeping, O--Oprah Magazine, Organic Gardening and other publications.