  In this talk we present the calculation of the neutrino self-energy in
presence of a magnetized medium. The magnetized medium consists of electrons,
positrons, neutrinos and a uniform classical magnetic field. The background
magnetic field is assumed to be weak compared to the $W$-Boson mass as a
consequence of which only linear order corrections in the field are included in
the $W$ boson propagator. The electron propagator consists all order
corrections in the background field. Our calculation is specifically suited for
situations where the background plasma may be CP symmetric.
