  The recent experimental measurements of the solar neutrino mixing angle
$\theta_{sol}$ and the Cabibbo mixing angle $\theta_C$ reveal a surprising
relation, $ \theta_{sol}+\theta_C \simeq \frac{\pi}{4}$. We note that the
lepton mixing matrix derived from quark-lepton unification can lead to a shift
of the complementarity relation at low energy. While the renormalization group
effects generally lead to additive contribution on top of the shift, in this
letter, we show that the threshold corrections which may exist in some
intermediate scale new physics such as supersymmetric standard model can
diminish it, so we can achieve the complementarity relation at a low energy.
Finally, we discuss a possibility to achieve the complementarity relation at a
high energy by taking particular form of non-symmetric form of down Yukawa
matrix.
