The talk of weight requirements reminded me that I never reported back!
In January, I tried to donate, and the nurse said (at 5'4 and 118lbs) that I was too light to donate, so they wouldn't let me. I emailed the UK Blood Service and asked if this was an actual legal requirement. Well, apparently, the nurse got it wrong.
In the UK, if you're a female, between the ages of 17 and 20, you need to weigh a certain amount (in relation to your height) in order to be eligible to donate. For my height I had to be at least 121lbs. However, after your 20th birthday, this stops being a requirement, and starts being more of a personal guideline (I'm not sure why - the email didn't explain). As I was 23 at the time, obviously the nurse was misinformed.
However, they do suggest that women who fall below the line don't donate unless they are sure they don't have adverse reactions. I did get dizzy after donations, even when I was well within the weight limits, so I guess I'm out, especially as I'm now only 115lbs.
Keep up the good fight, people! I'm going to carry on supporting the cause and urging other people to donate, but I think my blood is staying where it is.