Short answer: Not likely.

Long answer: If they think you're doing SI and have a plan to attempt suicide, then yes, they can/will report you. If they're in an organization which has policies around self injury, then maybe. Like if you were in a program that said if you SI you get kicked out - then they'd likely have to report it to someone. But to the police, not likely. If their notes get subpoenaed or they're under court order, then maybe - if they think your self injury makes you at risk and that you might be a bad parent, then if something like children's aid is involved - it could be reported because it could be dangerous for the child involved.

I'm in a social service worker program, the guidelines for breaking confidentiality are (but also include agency guidelines, which may be more extensive):

- Intent to harm yourself or others (serious bodily harm, which most SI is not. However if you're cutting near arteries or are at risk due to other preexisting health conditions that changes how serious the SI is considered)
- Abuse of a child, or a child at risk (or another vulnerable person at risk, like a senior citizen or someone who has a severe disability that makes them unable to care for themselves)
- Court order/subpoena