Blood Donation: Who Can Give and What Happens

Blood cannot be manufactured. Every unit used in surgery, after a road accident, for a mother bleeding after childbirth or for a child with thalassaemia comes from someone who sat down and gave it. Here is what donating actually involves.

Why do voluntary, unpaid donors matter?

WHO counts about 120.4 million blood donations collected worldwide, and recommends that countries build their blood systems on voluntary, unpaid donors. The reason is safety: WHO says infections carried in blood are least common in this group, which makes them the safest source of blood.

Supply is very uneven. WHO reports about 28.9 donations per 1,000 people in high-income countries, 18.2 in upper-middle-income countries, 8.5 in lower-middle-income countries and 4.5 in low-income countries. WHO also says every donation should be screened before use, and that testing for HIV, hepatitis B, hepatitis C and syphilis should be mandatory.

Who can give blood?

Exact rules are set by each country's blood transfusion service, so confirm with the centre you go to. As a guide, the UK's NHS blood service uses these limits:

• Age 17 to 65 for a first donation, and up to 72 for people who have donated before
• Weight between 50 kg and 158 kg
• Men can donate every 12 weeks; women every 16 weeks

Mayo Clinic adds that you should be in good health and not feeling unwell on the day you donate.

Who cannot donate, or should wait?

Based on NHS blood service rules, you will normally be told not to donate if you:

• Have tested positive for HIV, or are a hepatitis B or hepatitis C carrier
• Have had most types of cancer, an organ transplant, or certain heart conditions
• Have injected drugs that were not prescribed for you

And you will usually be asked to wait if you:

• Feel unwell on the day
• Are pregnant, or gave birth in the last six months
• Have had a tattoo or piercing recently
• Have travelled recently to places where certain infections are common

Being turned away is not a judgement on you. It protects you and the patient who would have received your blood.

What happens on the day?

1. Health check. Staff go through your medical history and check your blood pressure, pulse and temperature, and sometimes your weight.
2. Finger prick. A drop of blood is tested for haemoglobin, to make sure donating is safe for you.
3. The donation. A sterile needle is used to collect about half a litre of whole blood. Mayo Clinic says the collection itself takes about 10 minutes.
4. Rest and a snack. You rest for about 15 minutes with a drink and something light to eat before you leave.

Mayo Clinic suggests preparing by sleeping well, eating a healthy meal, avoiding fatty food, drinking plenty of water, skipping alcohol, and wearing sleeves you can roll up.

How should I look after myself afterwards?

• Drink extra fluids for the next 48 hours
• Avoid heavy exercise and hard physical work for 24 hours
• Keep the bandage on for two to three hours
• Eat iron-rich foods to replace the iron you gave

Mayo Clinic lists the common side effects as feeling lightheaded, which usually passes if you lie down, and bruising where the needle went in, which a cold pack for 20 minutes can ease in the first 24 hours.

When to see a doctor

Contact the donation centre or a doctor if, after donating, you:

• Keep feeling faint or dizzy even after resting, eating and drinking
• Have bleeding from the needle site that does not stop with firm pressure
• Have spreading redness, swelling, warmth or pain at the needle site
• Develop a fever in the days afterwards

Also tell the blood centre quickly if you realise afterwards that you were unwell or should not have donated, so the unit can be held back. If you faint and injure yourself, or have chest pain or difficulty breathing, call Rescue 1122 where available, or go to the nearest hospital emergency department.