Giving Blood???

I give twice a year.  I've never raced the next day but I have trained without any worries. For sure your A rafce won't be affected in the least.

As long as you eat well before and after donating, and remain well hydrated all day, you'll be fine. When we donate at work, we make sure to go right after lunch. Lunch is usually burritos, too. 

I think the pint of blood is about 10% of your average blood volume, so you'll be down about 10% of the oxygen carrying red blood cells for the 5K even as you've replaced the volume.  That will definitely affect your top-end performance. 

As for your race 5 weeks later...by then, your body should have replaced the missing red blood cells.  Whether it has completely recovered from that effort is subject to debate (there's a reason the waiting period is 8 weeks).  So the answer may be "it depends" (on the distance of your race, and what kind of performance you expect that day). 

I gave blood just a few weeks back and it affected my performance over about a week. I felt sluggish and like I couldn't hit anything over 80% when out running.

But then 11 days after giving blood I pr'd my half marathon so you should have time.

Exactly right!

All I know is that the 4 guys I work with who have been shot, 3 killed, took over 100 units while they were trying to be saved/were saved......I'd give the day before an IM if asked. 

It really is important.

You give, your race is not quite what you wanted it to be...........so what?

And yeah, I understand that everyone can't give for a variety of reasons....all the more important for those of us who can.  If you've never given, please consider it.

Funny that I'm seeing this thread as I just finished making an appointment for tomorrow!  

I donate double red blood cells pretty much every time I'm eligible and while I feel sluggish for a day or two, I don't really notice it after that.  Besides, I figure this is one small way that I can help others who might need it way more than I do.   

Excellent!