The U.S. Preventive Services Task Force recommends that all women start mammogram screening at age 40 and continue every other year through age 74. This updated guideline, finalized in 2024, replaced earlier advice that left the decision to start in your 40s up to you and your doctor. The recommendation now applies to all women at average risk, with earlier and more frequent screening for those at higher risk.
Current Screening Guidelines by Age
The two most influential organizations in U.S. breast cancer screening give slightly different advice, which can be confusing. The USPSTF recommends mammograms every two years from age 40 through 74 for all women at average risk. Previously, the task force said women in their 40s should make an individual decision about when to begin. That flexibility is gone: 40 is now the clear starting point.
The American Cancer Society takes a more granular approach. Women aged 40 to 44 have the option to start annual screening but aren’t told they must. From 45 to 54, the ACS recommends yearly mammograms. At 55 and older, women can either switch to every other year or keep going annually. The ACS also says screening should continue as long as a woman is in good health and expected to live at least 10 more years.
In practical terms, no major organization suggests waiting past 45 to begin. If you’re 40 and wondering whether it’s time, both sets of guidelines say yes.
Every Year or Every Other Year?
One of the biggest questions isn’t just when to start but how often to go. Screening every two years captures about 81% of the mortality reduction that annual screening provides, while cutting the total number of mammograms in half. That tradeoff is why the USPSTF landed on biennial screening as its default recommendation.
Annual screening does catch more cancers, but it also produces significantly more false alarms. Screening yearly from 40 to 74 results in roughly 50% more false positives and 50% more cases of overdiagnosis compared with every-other-year screening. Overdiagnosis means detecting a cancer that would never have caused symptoms or harm during a woman’s lifetime, but that still gets treated with surgery, radiation, or other interventions.
For women in their 40s specifically, the numbers illustrate why this age group generates debate. Out of every 1,000 women aged 40 to 49 who get a mammogram, about 121 will receive a false-positive result. Around 125 will be called back for additional imaging, and about 16 will be recommended for a biopsy. The screening will detect roughly 2 invasive breast cancers and 1 to 2 cases of early-stage abnormal cells per 1,000 women screened. Put another way, for every invasive cancer found in this age group, 464 women had mammograms, 58 were sent for additional imaging, and 10 underwent biopsies.
None of this means screening in your 40s isn’t worthwhile. Starting at 40 rather than 50 reduces breast cancer deaths by about 3%. That translates to roughly one additional life saved per 1,000 women screened. Whether that benefit outweighs the anxiety and procedures from false positives is a personal calculation, but the USPSTF decided the evidence favors screening.
If You’re at Higher Risk
Standard guidelines assume average risk. If you carry a BRCA1 or BRCA2 gene mutation, have a first-degree relative (mother, sister, daughter) with one of those mutations, or have a lifetime breast cancer risk of 20% or higher based on family history, screening should start earlier and include more than just mammograms.
The American Cancer Society recommends that women with BRCA mutations or a lifetime risk above 20 to 25% begin both annual mammograms and annual breast MRIs at age 30. The National Comprehensive Cancer Network goes further for BRCA carriers, recommending breast MRI starting as early as 25, with mammograms added at 30. For women with certain rarer genetic conditions, such as Li-Fraumeni syndrome, screening can begin at 20.
If a close family member was diagnosed with breast cancer at a young age, some guidelines recommend starting screening 10 years before the age that relative was diagnosed. So if your mother was diagnosed at 38, you might begin at 28, though generally not before age 25 for MRI or 30 for mammograms.
If you’re unsure of your risk level, a risk assessment tool (your doctor’s office can run one) uses your family history, reproductive history, and other factors to estimate your lifetime probability of breast cancer. That number determines whether you fall into the higher-risk category that benefits from earlier or supplemental screening.
When Screening May No Longer Help
The USPSTF guidelines stop at age 74, not because breast cancer risk drops after that age, but because the evidence on screening benefits becomes less clear while the harms become more significant. The risk of overdiagnosis climbs steeply in older women. For women aged 75 to 84, nearly half of screen-detected breast cancers may represent overdiagnosis, meaning cancers that would never have become life-threatening. For women with a life expectancy under five years, that figure exceeds 50%.
The American Cancer Society doesn’t set a hard upper age limit, instead tying the decision to overall health and life expectancy. If a woman is in good health and expected to live at least another 10 years, continued screening can still be beneficial. But for older women dealing with other serious health conditions or frailty, a breast cancer diagnosis and its treatment may cause more harm than the cancer itself would have. This is a genuinely individual decision, and reasonable people in similar health situations may make different choices.
Quick Reference by Risk Level
- Average risk: Start mammograms at 40, every two years through at least 74.
- Higher risk (20%+ lifetime risk or strong family history): Start mammograms and breast MRI at 30, annually.
- BRCA1 or BRCA2 carriers: Breast MRI starting at 25, mammograms added at 30, both annually.
- Li-Fraumeni syndrome or TP53 mutation: Screening can begin at 20.