Screening guide › Breast screening
Breast screening
Mammography through the Ontario Breast Screening Program (OBSP): an informed decision at 40–49, recommended for most at 50–74, with a separate high-risk program.
- Ages 40–49
- Eligible to consider; informed decision. If chosen, mammography every 2 years.
- Ages 50–74
- Mammography every 2 years recommended for most eligible people.
- High risk (30–69)
- Separate High Risk OBSP; generally annual mammography + MRI; referral required.
- Access
- Self-referral: 1-800-668-9304. No doctor's referral needed.
- Not routine
- Symptoms, previous breast cancer, abnormal result awaiting assessment, existing high-risk plan.
What this page helps with
A screening mammogram is a low-dose breast X-ray for people without symptoms. This page helps you understand whether routine breast screening applies to you, how Ontario frames the choice at different ages, and how to book it — including without a family doctor. It does not tell you whether you are due; that depends on your last mammogram and any prior results.
Symptoms are not screening. If you have new or concerning symptoms, arrange assessment rather than a screening test. Severe or life-threatening symptoms: call 911 or go to the nearest emergency department; otherwise a provider, walk-in or urgent care clinic, or Health811 (811).
Who the routine guidance is for, and who needs another pathway
OBSP screening is for people ages 40–74 who have an Ontario health card, no new breast symptoms, no personal history of breast cancer, no mastectomy, and no screening mammogram in the last 11 months. For transfeminine people, Ontario's published criterion includes at least five consecutive years of feminizing hormone use. Having breast or chest tissue does not by itself establish eligibility.
Ages 40–49. You are eligible to consider screening. Ontario encourages an informed decision, weighing your personal risk, the potential benefits and harms, and what matters to you — the balance can differ from that at 50–74. If screening is chosen, most people are screened every 2 years.
Ages 50–74. Ontario recommends mammography every 2 years for most eligible people. The program recalls some people yearly based on specific family-history patterns.
High risk. The High Risk OBSP (ages 30–69) has separate criteria — for example a known BRCA1/2 or similar gene variant, a first-degree relative of a known carrier, or a clinician-confirmed lifetime risk of 25% or more — and generally uses annual mammography plus MRI with a referral. A family history alone does not establish high-risk eligibility; a clinician assesses it. Someone already in a high-risk plan should keep to that plan rather than the ordinary two-year pathway.
Not routine screening. A previous breast cancer, an abnormal result awaiting assessment, or current symptoms follow a diagnostic or follow-up pathway set by your clinician. After 74, screening may continue with a referral as an individual decision.
How to access it in Ontario
You can self-refer to any OBSP site by calling 1-800-668-9304; no doctor's referral is needed. A family doctor or nurse practitioner can also refer you. If you are 40–49 and unsure, a Health811 navigator (811) can help you weigh the decision. If you have no primary care provider, the program can still screen you; see No family doctor?.
Potential benefits and limitations
Screening can find breast cancer before it can be felt, when treatment may be less intensive and outcomes better. It also has limits: some cancers are missed, some abnormal results turn out not to be cancer (leading to extra imaging or a biopsy), and some cancers found would never have caused harm (overdiagnosis). The balance of benefit and harm differs by age and personal risk, which is why Ontario frames 40–49 as an individual decision. Being "breast aware" — noticing changes and reporting them — is reasonable at any age, but it is not a substitute for screening and no formal self-examination schedule is required.
What the appointment involves
A mammogram takes about 15–20 minutes. Each breast is compressed briefly between plates for two X-ray images. It can be uncomfortable but is quick. Results are sent to you and to your provider; OBSP also sends reminders when the next screen is due.
What happens after an abnormal result
Most people with an abnormal screening result do not have cancer. The usual next step is further imaging (extra mammogram views or ultrasound), and sometimes a biopsy. OBSP coordinates this follow-up; do not use a new screening mammogram to investigate a result or a symptom. This page cannot interpret your result.
Questions to ask your provider
- Given my age and family history, how do the benefits and harms of screening balance for me?
- Do I meet OBSP criteria, and should I be assessed for the High Risk program?
- When was my last mammogram, and when would the next one be due?
- What should I do if I notice a change between screens?
Sources and when they were checked
- R07 — Breast Screening Recommendations Summary, Cancer Care Ontario / Ontario Health.
- R08 — Ontario Breast Screening Program (provider information), William Osler Health System. Cross-check only; provincial policy governs.