  Typically, fault-tolerant operations and code concatenation are reserved for
quantum error correction due to their resource overhead. Here, we show that
fault tolerant operations have a large impact on the performance of symmetry
based error mitigation techniques. We also demonstrate that similar to results
in fault tolerant quantum computing, code concatenation in fault-tolerant
quantum error mitigation (FTQEM) can exponentially suppress the errors to
arbitrary levels. For a family of circuits, we provide analytical error
thresholds for FTQEM with the repetition code. These circuits include a set of
quantum circuits that can generate all of reversible classical computing. The
post-selection rate in FTQEM can also be increased by correcting some of the
outcomes. Our threshold results can also be viewed from the perspective of
quantifying the number of gate operations we can delay checking the stabilizers
in a concatenated code before errors overwhelm the encoding. The benefits of
FTQEM are demonstrated with numerical simulations and hardware demonstrations.
