for UK … just copied from their site
[spoiler]You should not give blood if:
1 You’ve already given blood in the last 12 weeks (normally, you must wait 16 weeks).
2 You have a chesty cough, sore throat or active cold sore.
3 You’re currently taking antibiotics or you have just finished a course within the last seven days.
4 You’ve had hepatitis or jaundice in the last 12 months.
5 You’ve had ear or body piercing or tattoos in the last 6 months.
6 You’ve had acupuncture in the last 6 months outside the NHS (unless you can produce the approved certificate from your acupuncturist or physiotherapist).
7 A member of your family (parent, brother, sister or child) has suffered with CJD (Creutzfeld-Jakob Disease).
8 You’ve ever received human pituitary extract (which was used in some growth hormone or fertility treatments before 1985).
9 You have received blood or think you may have received blood during the course of any medical treatment or procedure anywhere in the world since 1st January 1980.
You may not be able to give blood if:
1 You’ve had a serious illness or major surgery in the past or are currently on medication. Please discuss this with the clinical staff. The reason you’re taking medicines may prevent you from donating.
2 You’ve had complicated dental work. Simple fillings are OK after 24 hours, as are simple extractions after 7 days.
3 You’ve been in contact with an infectious disease or have been given certain immunisations in the last four weeks.
4 You’re presently on a hospital waiting list or undergoing medical tests.
5 You do not weigh over 50kgs (7st 12).
You should not give blood if you are pregnant or you are a woman who has had a baby in the last 9 months.
Please wait 6 months after returning from a malarial area before giving blood. Please also tell us if you have visited Central/South America at any time. (Those who’ve had Malaria, or an undiagnosed illness associated with travel, may not however be able to give blood.)
West Nile Virus
Have you been to or plan to go to CANADA or the UNITED STATES this Summer? If yes, please click here, as it might affect you giving blood.
The special problem of HIV and Hepatitis viruses
• Every single blood donation is tested for HIV (the virus that causes AIDS) and hepatitis B and C.
• Infected blood isn’t used in transfusions but our test may not always detect the early stages of viral infection.
• The chance of infected blood getting past our screening tests is very small, but we rely on your help and co-operation.
• People who carry these viruses may feel healthy for many years.
You should never give blood if:
1 You carry the hepatitis B virus, the hepatitis C virus or the HIV virus.
2 You’re a man who’s had sex with another man, even safe sex using a condom.
For more information on why men who have sex with men cannot give blood click here
3 You’ve ever worked as a prostitute.
4 You’ve ever injected yourself with drugs - even once.
You should not give blood for 12 months after sex with:
1 A man who has had sex with another man (if you’re a female).
2 A prostitute.
3 Anyone who has ever injected themselves with drugs.
4 Anyone with haemophilia or a related blood clotting disorder who has received clotting factor concentrates.
5 Anyone of any race who has been sexually active in parts of the world where AIDS/HIV is very common. This includes countries in Africa.
Please do not give blood if you even think that you need a test for HIV or hepatitis, or if you had sex in the past year with someone you think may be HIV or hepatitis positive.
Never give blood to get an HIV test. [/spoiler]
I used to be a blood donor, but I can’t anymore due to taking medication.