The effects of high absorbed dose on the reusability of CaF²:Mn thermoluminescence dosimeters (TLDs) are investigated to determine a recommended upper limit on absorbed dose for TLDs that are to be reused. This investigation examines degradation in the uniformity of response and changes in sensitivity of a batch of TLDs when exposed to gamma-radiation doses ranging from 1 Gy to 1000 Gy, and confirms earlier work suggesting that CaF²:Mn TLDs should not be reused in applications where cumulative absorbed doses are likely to exceed 100 Gy.