There are rules about who can and cant donate blood. (Edit – these are AUSTRALIAN rules. the rules will vary in other countries. Sometimes Significantly. In the USA the Pay for blood donations for example. Thats considered unethical in australia for example and so on)….
They have been challenged and reviewed – with the last review being done (that I am aware of anyway) in May 2012.
The review is here http://www.bloodrulesreview.com.au/files/upload/blood_review_report_may_2012_electronic_version.pdf
The rules currently – are ….
You can never give blood if:
You are HIV positive
You have hepatitis B
You have or have had hepatitis C
You have ever injected yourself or been injected with drugs not prescribed by a doctor or dentist (even if this was only once)
You can not give Blood IF in the past 12 months, you have/or had:
Oral or anal sex with another man, even ‘safer sex’ using a condom (if you are a man)
Sex with a man who has had oral or anal sex with another man (if you are a woman)
Sex with a partner who has HIV or hepatitis C
Sex with a partner who has hepatitis B, unless you have been vaccinated and/or are immune on our testing
Sex with a partner who has ever injected themselves with drugs not prescribed by a doctor or dentist
Sex with a male or female sex worker
A blood transfusion, excluding transfusions of your own blood
Hepatitis or been in close contact with someone with hepatitis
Been in prison
Sex with anyone who lives in, or has come from, a country considered to have a high rate of HIV infection.
You must also
be fit, healthy and not suffering from a cold, flu or other illness at the time of donation or in the previous 7 days
be aged between 16-70 years (in QLD and WA 16-17 year olds require parental consent)
weigh more than 45kg
drink up in the 24 hours before donation, especially in warm weather and have at least 3 good-sized glasses of water/juice in the 3 hours before donating.
eat something in the 3 hours before donating
bring at least one form of photo identification ID.
There are also some restrictions based on travel (for example based on possible exposure to mad cow disease in the UK )
These details can be found on the red cross website http://www.donateblood.com.au/faq#faq_300
There is some background to this
Although Australia started screening Blood donations for HIV quite early – there were cases of transmission
(The story of one is given in Brysce Courneys Book – April Fools Day – -http://en.wikipedia.org/wiki/April_Fool%27s_Day_%28novel%29 Warning – I openly sob when I read this one)
Also there is a detection delay when newly infected people are carrying the virus but the tests will not pick it up…. I dont profess to be an expert on this matter BUT this should give some idea on the issue….