During a full blood donation, a person gives 450 ml of blood. That is about 10 percent of an adult’s blood volume. Giving this amount is safe and doesn’t typically cause any ill effects. Infrequently (e.g. 1 percent of donations at our Blood Centre) the donor may experience side reactions during or after the donation: weakness, dizziness, cold sweat, fainting and other symptoms).
Risks of adverse reactions can be increased by:
- not having eaten
- lack of sleep
- emotional stress (anxiety about the procedure, seeing blood or other donors giving blood)
- being tired
- pain during the needle insertion
Fainting or a feeling of faintness or dizziness can be caused by a drop in blood pressure.
Always make sure you are healthy, rested and have eaten before you give blood.
- to drink plenty of fluids before and after giving blood, including on the day after making a donation;
- to prefer lean and iron-rich food (red meat, liver, dark greens and colourful vegetables etc);
- the best time to give blood is two or three hours after you have eaten;
- if your blood pressure tends to be low, eat saltier food – increase your salt intake before and after the donation, as this will help raise your blood pressure;
- to consume plenty of fluids after giving blood as well; the Blood Centre offers complimentary tea, coffee and juice. And nibble on snacks – sweet cookies and salty biscuits;
- to rest after giving blood, before you go on with your everyday activities, and let your body get used to the lower blood volume;
- it’s advisable to avoid strenuous physical exertion on the day of the donation and the following day (working out, saunas, swimming) on the day you give blood and the day after.
Fainting while giving blood is usually caused by psychological factors, however.
To prevent this:
- avert your eyes from the syringe and blood receptacle;
- try to think about something else and stay positive – you are helping save lives when you give blood;
- the Blood Centre worker is by your side throughout the procedure and ready to help you if needed.
Tensing your muscles also keeps blood pressure from dropping: squeeze a rubber ball, periodically contract your gluteal and leg muscles.
After giving blood, you may feel faint if you stand up abruptly or if you have been standing for a long time.
If you feel that you are getting weak, then to avoid fainting:
- do exercises using your muscles: cross your legs, tense your muscles all over your body or your gluteal muscles – this will keep blood pressure from dropping;
- squat as soon as you feel faint;
- if possible. lie down and elevate your legs;
- consume salt (salty biscuits at the Blood Centre, salty meal after leaving the centre);
- consume fluids.
We hope that your donation is a pleasant experience and free of adverse effects.
The Blood Centre