  We derive the threshold corrections in $\mathrm{SO}(10)$ grand unified models
with the intermediate symmetry being flipped
$\mathrm{SU}(5)\times\mathrm{U}(1)$ or
$\mathrm{SU}(3)\times\mathrm{SU}(2)\times\mathrm{U}(1)\times\mathrm{U}(1)$,
with the masses of the scalar fields set by the survival hypothesis. These
models do not achieve gauge coupling unification if the matching conditions do
not take threshold corrections into account. We present results showing the
required size of threshold corrections for any value of the intermediate and
unification scales. In particular, our results demonstrate that both of these
models are disfavored since they require large threshold corrections to allow
for unification with a predicted proton lifetime above current experimental
bounds.
