function is_custom_post_type() {

	global $wp_query;

		
	$post_types = get_post_types(array('public'   => true,'_builtin' => false),'names','and');
	
	foreach ($post_types  as $post_type ) {
		if (get_post_type($post_type->ID) == get_post_type($wp_query->post->ID)) {
			return true;
		} else {
			return false;
		}
	}
}

Check if current post type is a custom post type – WordPress. 
Returns a true/false-statement.

Can be used outside The Loop.

Check if current post type is a custom post type – WordPress

php, post, wordpress

PHP