Do aspirin's blood thinning effects make it dangerous during my period?

No: Aspirin does not typically 'thin the blood' enough to make menstruation dangerous. If you notice you are bleeding very heavily during your period, you might consider visiting a doctor.

Aspirin: Aspirins platelet inhibition generally doesn't cause much increase in period bleeding. Some people have different clotting balance and if you are having heavy bleeding on asa, check with your doctor to discuss.