Form Alter: How to check if a node has a Field Type
If you are searching for specific field then see the code below 

 function hook_form_alter(&amp;$form, &amp;$form_state, $form_id) {
if ($form_id == 'form_id_name') { 
        $abc = array();
        foreach ( $form_state['field'] as $key =&gt; $value ) {
            $abc[$key] = $key;
        };
}
    }


From this $abc variable you will get all the field name and then you can check from this array to see if the field you want exists or not using any of the php functions.
For e.g.
you can use array_key_exists('field_name', $abc);