Getting tested for cancer starts with a conversation with your primary care doctor, who can order screening tests based on your age and risk factors or refer you to a specialist if you have symptoms. The process looks different depending on whether you’re checking proactively (screening) or investigating something specific (diagnostic testing), but both paths typically begin in your doctor’s office.
Screening vs. Diagnostic Testing
Cancer tests fall into two distinct categories, and understanding the difference shapes what happens next. Screening tests check for signs of cancer before you have any symptoms. They’re designed to catch cancer early, when it’s most treatable. A diagnostic test, on the other hand, is ordered when something has already raised a red flag: a lump you found, unexplained weight loss, abnormal bloodwork, or an unusual result on a screening test.
A screening test is not a diagnosis. If a screening comes back abnormal, your doctor will order follow-up diagnostic tests to determine what’s actually going on. Many abnormal screening results turn out to be benign. The goal of screening is to cast a wide net so that the small percentage of results that do indicate cancer get caught as early as possible.
Routine Screenings by Cancer Type
Several cancers have well-established screening guidelines tied to your age, sex, and risk level. If you’re at average risk, here’s what the major recommendations look like.
Breast Cancer
The U.S. Preventive Services Task Force recommends a mammogram every two years for women aged 40 to 74. This applies to cisgender women and all people assigned female at birth, including transgender men and nonbinary individuals. If you have a strong family history or other risk factors, your doctor may recommend starting earlier or screening more frequently.
Colorectal Cancer
Screening is recommended for all adults aged 45 to 75. You have several options. A stool-based test like the fecal immunochemical test (FIT) is done at home once a year. A stool DNA test is done every three years. A colonoscopy, the most thorough option, is needed only every 10 years for people at average risk. Your doctor can help you choose based on your preferences and history.
Lung Cancer
Yearly low-dose CT scans are recommended for adults aged 50 to 80 who have a smoking history of 20 pack-years or more and either still smoke or quit within the past 15 years. A pack-year means averaging one pack per day for one year, so someone who smoked two packs daily for 10 years would also meet the 20 pack-year threshold.
Prostate Cancer
There is no universal recommendation for prostate screening. Instead, men are encouraged to have a direct conversation with their doctor about the pros and cons of PSA blood testing, particularly starting around age 50 (or earlier for Black men and those with a family history). The decision is individualized because PSA testing can lead to follow-up procedures for slow-growing cancers that may never cause harm.
What Screening Costs You
Under the Affordable Care Act, all Marketplace health plans and many employer plans must cover recommended cancer screenings with no copay, coinsurance, or deductible. This includes colorectal cancer screening for adults 45 to 75 and lung cancer screening for eligible high-risk adults aged 50 to 80. Mammograms are also covered. If you’re uninsured, community health centers and some hospitals offer free or reduced-cost screening programs.
Blood Tests and Tumor Markers
Blood tests play a supporting role in cancer detection, though they rarely confirm a diagnosis on their own. Tumor markers are substances produced by cancer cells or by the body in response to cancer. A PSA test measures a protein linked to prostate cancer. CA-125 is associated with ovarian cancer. CEA is used primarily in colorectal cancer. These markers are most useful for tracking how a cancer responds to treatment or detecting recurrence, not as standalone screening tools. Elevated levels can also result from noncancerous conditions, so an abnormal result always requires further investigation.
You may have heard about multi-cancer early detection blood tests (sometimes called liquid biopsies) that claim to screen for dozens of cancers at once. As of 2025, none of these tests have been approved for clinical use. They’re still in clinical trials, and their real-world accuracy and usefulness remain uncertain.
Imaging Tests: CT, MRI, and PET Scans
When your doctor needs to see what’s happening inside your body, imaging is the next step. CT scans create detailed cross-sectional images and are often the first imaging tool used to locate a suspicious mass and measure its size. MRI uses magnetic fields instead of radiation and provides especially sharp images of soft tissue, making it valuable for brain, spinal, and pelvic cancers.
PET scans work differently. They detect metabolic activity rather than just structure. Cancer cells burn through energy faster than normal cells, so they light up as bright spots on PET images. This makes PET scans particularly useful for determining whether cancer has spread to other parts of the body. In practice, PET scans are almost always combined with a CT or MRI to overlay metabolic information onto a detailed anatomical map. PET can sometimes detect abnormal cell activity before a tumor is large enough to show up on CT or MRI alone.
Biopsies: Confirming a Diagnosis
Imaging and blood tests can raise suspicion, but a biopsy is what confirms whether cells are cancerous. During a biopsy, a small sample of tissue is removed and examined under a microscope by a pathologist.
The most common approach is a needle biopsy. A fine-needle aspiration uses a thin needle to withdraw a small cluster of cells. A core needle biopsy uses a slightly wider, hollow needle to extract a cylinder of tissue, giving the pathologist more material to work with. Both are typically done in an outpatient setting. You may receive a local anesthetic or a mild sedative, depending on the location. Most people can go home the same day, though you may need someone to drive you and help around the house for a day or two. Minor soreness and some drainage at the biopsy site are normal. Bleeding that doesn’t stop with gentle pressure warrants a call to your doctor.
For deeper or harder-to-reach areas, a surgical biopsy may be needed, which involves a small incision and sometimes general anesthesia. Your doctor will explain what to expect based on the specific location.
When Genetic Testing Makes Sense
Some people carry inherited gene changes that significantly raise their lifetime cancer risk. The most well-known are BRCA1 and BRCA2 mutations, which increase the risk of breast, ovarian, pancreatic, and prostate cancers. Genetic testing can identify these changes, but it’s not recommended for everyone.
You’re more likely to be a candidate for genetic testing if you have:
- A family member with a known BRCA1 or BRCA2 mutation
- Ashkenazi Jewish heritage
- A personal or family history of breast cancer diagnosed at age 50 or younger
- A personal or family history of ovarian cancer, male breast cancer, pancreatic cancer, or aggressive prostate cancer
Testing usually begins with a genetic counselor who reviews your family history and helps you understand what the results could mean for you and your relatives. If a harmful mutation is found, your doctor can recommend a more intensive screening schedule or preventive measures tailored to your specific risk.
How to Start the Process
If you have no symptoms and just want to stay on top of routine screening, schedule a visit with your primary care doctor and ask which tests are appropriate for your age and risk profile. Bring your family health history if you can, especially any cancer diagnoses among parents, siblings, or grandparents.
If you’re experiencing symptoms that concern you, such as unexplained weight loss, persistent pain, a new lump, changes in bowel habits, or unusual bleeding, tell your doctor exactly what you’ve noticed and how long it’s been going on. They can order initial tests in-house or refer you to a specialist such as an oncologist, gastroenterologist, or surgeon depending on the area of concern. The referral process moves faster when you provide specific details about your symptoms and timeline.