Racing after giving blood

I'm doing Kenley 10k this Sunday - originally scheduled for a couple of weeks ago, but postponed due to the icy weather. I'd planned a hard race as part of my buildup towards a PB attempt at Hastings half marathon. But.. I had an appointment to give blood on Monday, so when the race was postponed I decided to use it as a training run and not push for a good time. 

But.. I had a good run the other day and am going to test out some faster running on my run today, to see how I feel. Have been a bit tired going up hills, but otherwise fine generally - and the race is flat. I'm in a good spell of training - I'm tempted to push it on Sunday and see how it  goes.

Has anyone experience of racing after giving blood? Trawling through old threads, the general consensus has been to take it easy in training and play it by ear. I should be sensible... should I?

See how you feel - I gave blood a few years ago and found I was OKish on easy runs, but I was unable to maintain any resemblance of normal pace. I was something like a minute a mile slower for a given HR level, and was unable to get anywhere near 10k pace.  This lasted a couple of weeks for me and I've avoided giving blood since.  

Have you got an HR monitor?  If you do us it and try running based on HR rather than pace and see what pace you can maintain.

usually takes 24 hours to make up blood volume again , your fit and healthy , don't over do it, you'll be fine in a few days 

the red blood cells will be a few short until volume replaced, this may affect O2 levels and demand placed on them while exercising 

plenty of fluids, eat well i am sure you will be fine , 

i gave blood and fainted 3 hours later (rather dramatically in the school playground collecting my daughter, whose friends told her i had died!!!)  my body was displeased with lack of volume, i hadn't even exerted myself, a good sleep , fluids and food i was fine the next day  - i hope my unit of blood went to good use somewhere 

i have been put off since , as helpful as giving blood is, i felt awful that day although am fitter and heavier now, so maybe i would be fine? 

don't over do it 

Useful advice, thanks everyone. In my run today, when I pushed it a bit more, although I generally felt the same as normal, I really felt my heart beating a lot faster than normal when I stopped to cross roads etc. Strange but it does make sense now - the same amount of oxygen is being demanded of fewer red blood cells, hence the heart has to pump faster to give the same supply?

I think on Sunday I'll do what I've always wanted to do in a race sometime - take my watch off my wrist and run according to feel, monitoring posture and effort rather than pace. Will push it a bit and see what happens...

just in case you're interested - I ran today, ignoring my watch as planned, and was about 3-4 minutes off what I'd like to do for 10k at the moment. Conditions were fairly poor (pretty wet and windy, with the wind blasting across the airfield we were running around!) so I'd say that probably accounted for at least a couple of minutes anyway. All in all, I'm pretty happy now back to the training...