Downtime between donating blood

[mittu]

Reading this thread I noticed that in America you can donate blood every 8 weeks.

www.redcross.org confirms this:

To give blood for transfusion to another person, you must be healthy, be at least 17 years old or 16 years old if allowed by state law, weigh at least 110 pounds, and not have donated blood in the last 8 weeks (56 days).

However, in the U.K. the downtime required between donations is double the length as confirmed by The National Blood Service (www.blood.co.uk):

Q How often can I give blood?
A 3 times a year, which comes to roughly every 16 weeks.

So, why such a significant difference? Of course, the reason for the downtime is to allow the body to regenerate the blood lost during the donation and www.blood.co.uk states that fluid donated will be replaced “in a very short period of time” so why the need for such a lengthy gap in the U.K.?

I am presuming there is a good reason for it, blood is always needed and i’m sure there are plenty of people in the U.K. who would donate every 8 weeks if they were able to so what is the reason for doubling the downtime? Why can Americans give blood twice as often as the British?

Sorry to continue the current GQ theme of “Why do different countries work differently?” but it does seem very strange to me.

[Padeye]

There may not be any more reason than different sets of criteria were used in each country to determine safe maximum frequency of donations. The UK may just have a wider safety margin.

@mittu

www.blood.co.uk states that fluid donated will be replaced “in a very short period of time” .

Fluid != blood

Plasma is quickly regenerated which is why one can donate that component as frequently as twice a week. Red blood cells take longer to regenerate.

[mittu]

I guess “fluid” is something of an ambiguous term but supposing it is down to different theories on the time needed to regenerate blood, who is right? It seems odd to me that such a frequently occuring medical practice would be open to so much speculation.