Last Wednesday I did something that took me years to work up the courage to do. I went to the Canadian Blood Services clinic to donate blood. I figured that after a PICC Line and an NG Tube, I could handle this no problem. After filling out the paper work and getting my finger pricked to test my iron levels I was denied based on having slightly low iron. However, the nurse still brings you into a private interview room to explain how to get your iron levels up. During that conversation I discovered that if you are on iron supplements due to your doctor's orders, they won't take your blood because they don't want to counteract what your doctor is doing (building up your blood levels).
Then when I mentioned that the iron supplements were related to my Crohn's disease, she then looked up Crohn's in her binder and discovered that people with Crohn's are 'indefinitely" barred from donating because it would be a danger to the individual. If you had a flare-up or intestinal bleeding, they don't want you to be weakened by giving blood. Too dangerous.
So, there you have it. Got Crohn's? No donating blood for you - at least not in Canada.