  We study the electroweak vacuum stability in Type I seesaw models for 3
generations of neutrinos in scenarios where the right-handed neutrinos have
explicit bare mass terms in the Lagrangian and where these are dynamically
generated through the mechanism of spontaneous symmetry breaking. To best
highlight the difference of the two cases we concentrate on the absolute
stability of the scalar potential. We observe that for the first scenario, the
scale at which the scalar potential becomes unstable is lower from that within
the Standard Model. In addition the Yukawa couplings $\mathbf{Y}_\nu$ are
constrained such that $\Tr{[\mathbf{Y}^{\dagger}_\nu \mathbf{Y}_{\nu}}]
\lesssim10^{-3}$. In the second scenario the electroweak stability can be
improved in a large region of parameter space. However, we found that the
scalar used to break the lepton number symmetry cannot be too light and have a
large coupling to right-handed neutrinos in order for the seesaw mechanism to
be a valid mechanism for neutrino mass generation. In this case we have $\Tr
[\mathbf{Y}^\dagger_{\nu} \mathbf{Y}_\nu]\lesssim 0.01$.
