As a general point of view, it may be quite a good idea - the thinking being that if your body is as close to "normal" levels as possible pre-surgery, then that can only help in the post-operative period.
The key would be to check where your Hb levels are pre-surgery - if >10.0, then it may not help so much, but below 10.0 it could be a good idea.
Rgds
Poirot