How to examine existing field values and modify other field in hook_form_alter? I have a content type with a bunch of fields attached.  When displaying the node edit form I want to hide or display one field ( using $form['some_field']['#access'] = FALSE; ) if another field has a specific value.

I am using hook_form_alter() and would expect to find existing field values within $form_state['values'] but this key isn't present even though the form fields do contain existing previously saved field values.

What am I missing ?

Thanks
In node edit form $form_state['node'] contains full node object , from which will get the existing field values.