Had a bit of a 'mare at work earlier this week which meant that the only ride I could fit in was on the same day as donating blood.

I waited for 6/7hrs and drank plenty of fluid but was (stupidly) surprised at how cr@p I felt…obvious I know, but it was like riding with flu. Really sluggish, managed 7/8 miles (about half a typical ride) and missed out all of my big climbs.

I know it takes time to replace the lost fluid but does anyone know how long it takes to reestablish the blood quality so I can plan on my next 'enthusiastic' ride again?

I don't think that anyone will be able to give you a standard single answer to that, grtdkad (but, no doubt, somebody will). It depends on your level of fitness and general health really. There are 2 main things to consider – your circulating volume and the concentration of your red cells (which in turn determines your ability to carry oxygen to the parts that need it).
Think of an analogy with a pint of squash. If you tip a little bit out (say, 10%), you're left with less concentrate and less volume (because a bit of the concentrate went out with the bit that you tipped out). If you top up from the tap, the volume is replaced but what's left is a more dilute squash. That sudden drop in dilution (as opposed to a slow decline as happens when you slowly become anaemic with some diseases) can be noticeable immediately afterwards and what you'll notice is tiredness, feeling "washed out", longer recovery time and even a little short of breath. It could take several weeks for the level of concentration of your "squash" (i.e. blood) to get back up to normal as the red cells are produced to top up but there are a number of factors that could influence that.
I wouldn't personally do exercise immediately after giving blood and would bank on reduced performance for a couple of weeks afterwards – and no competitions in that time – as a rule of thumb. But that's just me. Listen to your body and do what's comfortable. There are ways of quantifying it and measuring your performance etc but that's out of the realms of leisure cyclists. I'm sure that any sports physiologists, anaesthetists or haematologists on here will be able to elaborate.
Apologies if the squash analogy is confusing, but hope that it helps.

Don't want to hijack the thread, but would this analogy also apply to platelet donation? I'm due to go and get tested to see if I'm suitable next week.

When I've given blood I've only every felt a bit rubbish for the rest of that day, but I've never tried exercising immediately after …

A lot of it is theoretical really. Although it will take time to replenish your red cells (whereas volume replacement will be a lot quicker), it depends on your reserve capacity. If you're towing a caravan with a 200cc bike and somebody lops off 20cc, you'll notice it a lot more than if you're towing the same caravan with a 6L Jag and somebody lops of the same 20cc. Thus if you're young and fit with no known (or hidden) health problems then after the immediate donation period is over, you may feel ok, although your peak performance would suffer for a while longer (if you were to push it that far).

Secret squirrel – The red cells are returned when you donate platelets so your oxygen carrying capacity shouldn't be affected. For this reason, you can donate platelets more often than whole blood. Platelets are involved in the clotting process. Still sensible to take it easy, listen to your body and not plan any competitions immediately afterwards, though, I would say. I would expect the effects of platelet donation to be less noticeable than donation of whole blood from the perspective of exercise alone.

We recently undertook a study investigating the effects of blood donation (~450 ml) on subsequent exercise tolerance and the parameters of endurance performance.

We did not specifically look at how long it takes the body to recover from this blood loss, as we undertook all experimental testing within four days of donation. However, from our venous blood measurements, the haem based constituents of the blood (i.e. Haemoglobin and the derived parameter haematocrit) do not recover, indeed they get proportionally worse (due to plasma volume shifts) within this four day period.

Physiologically, the reduction in haemoglobin reduces the oxygen carrying capacity of the blood. This effect serves to reduce VO2max (by ~10%) this in turn limits the VO2 kinetics (this stuff is a bit science heavy so I won't go into details here). The combination of these factors are bad news for exercise tolerance, which was reduced by ~22% during this study.

There is not a lot you can do to increase recovery, drinking water will help to replace your blood volume, but will dilute the red cell concentration (as Tinners mentions) and we showed experimentally. During previous EPO studies, the ingestion of ferritin (as iron tablets) has been suggested to help the body increase haemoglobin production. Although, erythropoesis (natural EPO production) appears to only really begin ~5-7 days post donation. With this in mind, there is not mcuh you can really do, just sit tight, your performance will return as your body naturally recovers.

Jon

When I was a student we used to go drinking after giving blood 🙂

MY mate has given blood for years and ridden after with seemingly no ill effects but recently its taking it out of him for a few days after giving blood. He thinks its age catching him up as he's nearly fifty 😉

last time i gave blood I played squash an hour later. I still won despite refusing to move more than a couple of steps from the centre T.

but yeah, it depends.

He was a Jag, but he's turning into a moped……….

tinners the unstoppable analogy machine! 🙂

Thanks all (the analogies work for me)!

I too have given blood for many years but this is the first time that I have registered a tangible change in energy levels – 'feeling flu-like' when riding. I really could not face my local climbs.

I guess it's reasonable, but thanks for the confirmation, I was starting to wonder whether it was just in my head. In the meantime I'll give it a couple more days (I felt out of breath just this morning riding my son's DMR up-hill at the local 'jump' centre).

I ride to and from chemotherapy. They take a sh*tload of blood from me on the day.

Quite frankly, I only do it for the steriod hit. I think I must have been pushing 70mph through Brixton on the A23 the other day!

In the interests of honesty, I bonk like a fat kid without cake when I get home…

The first and last time I gave blood, I felt great for about 5min then i blacked-out after my biscuit and done the shakin' stevens on the floor of the clinic. All the students doing their bit were freakin' out!
The old boy who works there caught my head just before it hit the floor…reflexes like a fox!

After that they told me they don't want me back again.

Still had a few pints that evening…cheap night 😉