More people need to give blood, but not everyone can. If you're one of the lucky ones who are able to donate, you should, says Lisa Marks

In October 1990 I underwent major spinal surgery. During the course of my seven-hour-operation I lost about eight pints of blood. I remember wondering who had taken the time to donate their blood so I could get well. I vowed there and then to give it back.

Last year the National Blood Service collected 2.1 million donations from about 1.6 million donors. It sounds a lot but it isn't. That's only five per cent of the population giving two or three times a year. And 8000 units of blood are needed every day to meet demand ? that?s 2.9 million units and rising.

Even so, blood donation sessions are busy and it's wise to book your appointment. Turning up at my local church hall was like stepping back in time. There was a real 'wartime' spirit as the nurses flitted between the ten beds. A group of donors, of both sexes and all ages, sat waiting.

There are many strict rules for blood donation - you are required to fill in a detailed medical form. In addition, I was given a folder full of rules and regulations and told to read them through carefully. Reading the updated book, it quickly became apparent that I wouldn't be able to give blood. Earlier this year the NBS brought in a new rule for blood donors. Because of the risk of vCJD (variant Creutzfeldt-Jakob disease), they can no longer accept donations from people who have received blood since January 1980. As the session doctor explained to me, 'We have to be extra careful. This is a precautionary measure only, so we'll keep you on our books in case this rule changes.'

I was completely deflated but Jane, 34, who was also in the waiting room, was able to donate. Her reasons were simple. 'I want to help and you never know when you might need some back,' she explained. 'Also, my mum had an operation recently and I remember thinking how amazing it was that these bags of blood seemed to appear like magic whenever she needed it.'

Giving blood takes under an hour. It's vital that you eat beforehand. Donating blood isn't bad for you but it can make you feel weak - hence the biscuits afterwards. Once you've filled in your forms, the nurse takes a drop of blood from your fingertip. This is to check that giving blood won't make you anaemic. Then you are painlessly hooked up to a bag which holds about 475ml (just under half a litre) of blood. Once the process is finished you get a biscuit and a drink. The nurses make sure you feel well, and then you are free to leave.

The hall was still packed with donors waiting their turn as I left with all my blood intact. But Sarah, 39, a blood donor returning for the third time, said, 'It makes me feel good to give blood. It takes very little time and it doesn't hurt. Honestly, it's not just for the biscuits!'

Who can give blood?
Not everyone can give blood - although some donors may simply be under a time restriction. For example, you'll have to wait clear 12 months to give blood after having a tattoo or piercing. Here are some questions you will be asked before you can donate:

• Are you aged between 17 and 59?
• Have you already given blood in the last 16 weeks?
• Are you pregnant or have a baby less than nine months old?
• Have you got a chest cough, sore throat or active cold sore?
• Are you taking antibiotics now, or have done in the last seven days?
• Have you had acupuncture, ear piercing, body piercing, tattooing or semi-permanent make-up in the last 6 months?
• Have you received blood since 1st January 1980?
• Has a member of your immediate family suffered with CJD?
• Are you HIV positive or do you think you might be?
• Have you had hepatitis or jaundice in the last 12 months?
• Are you a carrier of the Hepatitis B or C virus or think you might have hepatitis?
• Are you a man who has had oral or anal sex with another man (even if you used a condom)?
• Have you ever received payment for sex with money or drugs?
• Have you ever injected or been injected with drugs including body-building drugs (even if it was a long time ago or only once)?
• Have you had sex in the last 12 months with someone who is, or may be, HIV positive or a carrier of hepatitis B or C?
• Have you had sex in the last 12 months with a man who has had oral or anal sex with another man?
• Have you had sex during the last 12 months with someone who has received payment for sex with money or drugs or someone who has injected drugs including body building drugs?
• Have you had sex during the last 12 months with someone who has been sexually active in parts of the world where AIDS/HIV is very common?
• Have you had a serious illness or major surgery in the past or are you on medication at present?
• Have you had complicated dental work?
• Have you been in contact with an infectious disease or been given certain immunizations in the last 8 weeks?
• Are you presently on a hospital waiting list or undergoing medical tests?
• Have you been outside the UK (including business) in the last 12 months?
• Have you ever had malaria or an unexplained fever associated with travel?
• Have you ever stayed outside the UK for a continuous period of 6 months or more?
• Have you visited any malarious area in the last 12 months?
• Have you ever visited Central/South America for a period of 4 weeks or more?