In reply to Lhod:
I can remember noticing the difference running when I used to give blood, but a better "test" was using the rowing machine, going off at my normal pace and seeing how long I lasted - not long.
IIRC the rough thinking I heard years ago was:
- Blood back to full liquid volume - within a couple of hours at most if you're not dehydrated to start
- Red blood cells - a week
- White blood cells - a month
- Platelets - 3 months
Obviously, all of these are on "diminishing return" curves, e.g. you'll have 50% back within maybe 25% of the time, 75% back within 50% of the time, etc (made up figures purely to illustrate the idea).
So, after a week I guess you have to find something else to blame - I have a large collection if you need to borrow a performance excuse 😁