Higgs inflation can occur if the Standard Model (SM) is a self-consistent effective field theory up to inflationary scale. This leads to an upper bound on the top Yukawa coupling, y t phys < y t crit and thus on the mass of the top quark m t . If m t is more than a few hundred of MeV below the critical value, the Higgs inflation predicts the universal values of inflationary indexes, r ≃ 0.003 and n s ≃ 0.97 , independently on the SM parameters. We show that in the vicinity of the critical point y t crit the inflationary indexes acquire an essential dependence on m t and on the mass of the Higgs boson M h . In particular, the amplitude of the gravitational waves can exceed considerably the universal value.