If your numbers are really off, you can give two whole blood donations within a week or two. Obviously, this is not very good for you. They have that 56 day rule for a reason. You have to pick two separate blood donation organizations, they don't cross check. You would only do this of your Hemo was up approaching 20 ... which is a disaster but can happen. If this was the case, you would need more than one donation to get on track (and the Red Cross folks might even decline to take the blood).
One problem with these kinds of rapid donations is that you can deplete your iron stores (ferretin). Even though your Hemoglobin and Hematocrit will be back in the normal range, your ferretin levels can take a hit.
Just to get a data point, in my last blood test I checked my ferritin levels:
108 ng/mL (reference range 30 - 400)
About 4 years ago I needed a rapid set of donations to get on track. It worked and the local doc did not even notice. I did not check the ferritin levels at that time - but I can see they are generally OK now.