This minimum weight is set because a standard amount of blood is taken for all donors (450 ml).
Women are advised to give blood no more than three times a year; men, no more than four. Donors must also wait at least two months between donations.
Unlike when you go for a blood test, you can eat and drink before you give blood. In fact, it is best to have a normal meal before giving blood.
For the safety of both the donor and the recipient, a series of tests are carried out before the blood is taken and the donor's medical details are recorded. Afterwards, the blood itself is tested.
You can give blood:
Women can give blood up to three times a year; men, up to four.
The first stage in assessing whether a person can give blood is to ask them to answer a questionnaire aimed at identifying any possible risk factors. These questions are required by law and are aimed at looking after the safety of donors and future recipients.
Answering "Yes" to any of the questions does not necessarily mean that a donor will not be able to give blood. The doctor on duty will decide whether to go ahead with the donation.
A PDF of the questionnaire can be found below.