  We study the high-scale validity of two kinds of two Higgs doublet models
(2HDM), namely, Type-II and Type-X, but with a scalar SU(2) singlet dark matter
(DM) candidate in addition in each case. The additional quartic couplings
involving the DM particle in the scalar potential in both the scenarios bring
in additional constraints from the requirement of perturbative unitarity and
vacuum stability. DM relic density and direct search constraints play a crucial
role in this analysis as the perturbative unitarity of the DM-Higgs portal
couplings primarily decide the high scale validity of the model. We find that,
within the parameter regions thus restricted, the Type-II scenario must have a
cut-off at around $10^6$ GeV, while the Type-X scenario admits of validity upto
the Planck scale. However, only those regions which are valid upto about $10^8$
GeV in Type-X 2HDM is amenable to detection at the High-luminosity LHC (upto
3000 $fb^{-1}$), while most of the parameter space of the Type-II scenario
mentioned above is likely to be detectable.
