Erik Menendez Diagnosed with 'Serious Medical Condition'

12:49 PM PT -- Erik Menendez is undergoing treatment for kidney stones ... TMZ has confirmed.

Erik Menendez is battling a health issue that is so serious his lawyer is asking California Governor Gavin Newsom to release him immediately, ahead of next month's parole hearing.

Attorney Mark Geragos was on "TMZ Live" Tuesday and told Harvey Erik's medical condition is "serious" ... serious enough to warrant immediate action by the Governor.

Geragos said Erik is getting treatment in prison, but -- although Geragos wouldn't say -- it seems treatment by specialists outside the prison would be appropriate and possibly essential.

Erik and Lyle Menendez are scheduled for a parole board hearing August 22, but that process could be accelerated for Erik.