The primary decay mode before the most abundant stable isotope, 164Dy, is electron capture, and the primary mode after is beta decay.
Dysprosium is the heaviest element to have isotopes that are predicted to be stable rather than observationally stable isotopes that are predicted to be radioactive.
The radioactive isotope 165Dy, with a half-life of 2.334 hours, has radiopharmaceutical uses in radiation synovectomy of the knee.
It had been previously performed with colloidal-sized particles containing longer-lived isotopes such as 198Au and 90Y.
The major problem with the usage of those isotopes was radiation leakage out of the knee.