You should be able to give blood for you own personal use if need be. I cannot as i clot to quickly and it takes a very long time to get blood out just 4 all the normal tests. I don’t have many visible veins left to take blood from. Cah does play a big part in donating blood because of the steroid levels in the blood and it takes alot of work 2 normalise bloods to normal use. So that would be a possible reason for not been able to give.  Good luck with everything else.