  We explore the Renormalization Group flow of massive uncharged fermions -- a
candidate for dark matter -- coupled to a scalar field through a Higgs portal.
We find that fermionic fluctuations can lower the bound on the scalar mass that
arises from vacuum stability. Further, we discuss that despite the perturbative
nonrenormalizability of the model, it could be ultraviolet complete at an
asymptotically safe fixed point. In our approximation, this simple model
exhibits two mechanisms for asymptotic safety: a balance of fermionic and
bosonic fluctuations generates a fixed point in the scalar self-interaction;
asymptotic safety in the portal coupling is triggered through a balance of
canonical scaling and quantum fluctuations. As a consequence of asymptotic
safety in the dark sector, the low-energy value of the portal coupling could
become a function of the dark fermion mass and the scalar mass, thereby
reducing the viable parameter space of the model.
