Inside the loop you already have a
$post object available to you, you don't need to call
get_post_type or any other functions, this should do the trick.
<?php echo $post->post_type; ?>
Or if you like the idea of calling
get_post_type you can make the task easier for the function by passing it the post object you have(so it doesn't need to go fetch the post, just to extract one property from it).
<?php echo get_post_type( $post ); ?>
get_post_type will needlessly call
get_post to fetch the post object (an object you already have available to you nonetheless).
Hope that helps..