Moving from light to medium strings

[olie]

If I were to change from D'Add EJ 16 light strings to the medium of the same brand would it necessitate an adjustment to the nut or could I expect the same intonation, etc.?

[jedzep]

I don't think the nut would come into play, but your neck relief and action might change.  Adjust after it settles in to the new tension, or...what I do is play all with mediums, tuned down to D-D standard.  It gives you a couple extra keys to mess with and adds just enough extra torque to push the top a step up without making it too hard on the fret hand.

[Kwlsky]

I think it depends how your wide your nuts slots were made. I always slot mine .002-.003" wider than the 12-54s I use, so mediums would fit if I wanted to change. If your nut was slotted to fit only lights, you might need to widen them.  You could put mediums in and use a magnifying glass to see if the strings are sitting nicely at the bottom of the slots before you pin them into the bridge.   Also, if they don't fit right, you'll probably noticing them binding up when you tune them. +1 on the probable neck relief adjustment.