But not too much water. I've been on Tagrisso for 2 1/2 months. My body appears to still be adapting to this drug. Two weeks ago my sodium count went down to 125 (133 is normally the minimum end of normal.) My doctor ordered me to cut down to no more than one quart of water a day. I now add electrolytes to all the water I drink (Elete) and restrict to two quarts a day. An hour and a half from now I'll have my third weekly blood test.