Can I self level a bathroom floor without removing the bath sink and toilet?

yes you can all you need to do is go to Lowes and buy some self leveler in the flooring department, just know that if you don't go wall to wall with it could crack and make a mess also I would advise to spread on concrete adhesive before using. If you have a wooden floor you can use treated 2x2 and lay them down 16" apart and put at least 12 inch plywood on top furring it to the end