Everything you need to know about giving blood

Last updated:
Reviewed by:
Lead GP at Livi Dr Rhianna McClymont
Dr Rhianna McClymont, Lead GP at Livi
Blood donations: everything you need to know when you give blood
Every day, hospitals rely on a generous number of blood donations to meet the needs of thousands of patients, either in an emergency or who are having continuous medical treatment. Dr Rhianna McClymont shines a light on why giving blood is so important.

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To meet the demand for blood donations, the UK needs 5,000 people to give blood every day.

There are lots of reasons why someone might need a blood transfusion, and one of these is blood cancer. Blood cancer is the fifth most common cancer in the UK, with over 40,000 people being diagnosed in the UK every year. It’s also the most common childhood cancer, with over 500 children (under 15) diagnosed with blood cancer every year. The most common blood cancers are leukaemia and lymphoma.

‘As September is National Blood Cancer Awareness Month, we want to help raise awareness of how important it is to give blood if you can,’ says Dr Rhianna McClymont, Lead GP at Livi.

‘We’ve tried to list everything you need to know about giving blood if you’re perhaps considering it for the first time.’ In the UK, there’s currently a greater need for male donors to give blood (and men can actually donate more often than women), black donors and O negative donors.

Why might I need a blood donation?

Blood donations are crucial to treat patients who have suffered a significant loss of blood – either from having a serious accident, surgery, childbirth or if they have a medical condition like anaemia, cancer or blood disorders such as haemophilia.

O negative is the blood type used most in emergencies and across hospitals in the UK. Because it can be given to anyone, it’s seen as the most 'prized' blood type. Other blood types have to be a much closer match – so someone with blood type A positive would need to be given to an A positive type recipient.

There’s also a higher demand for blood donations from black donors to treat black patients with sickle cell disease. It’s crucial for their treatment to have blood transfusions from black donors as a closest match to their blood.

Can I give blood?

‘Most people are able to give blood, but it’s worth speaking to a GP or checking the restrictions online if you’re not sure. These cover any issues with your health, medication you take, and whether you've been abroad recently,’ says Dr McClymont.

To find out if you’re eligible to give blood, you can visit the UK’s blood donation website and search the Health and Eligibility sections.

It will take you through some interactive questions – based on the most common reasons people are unable to give blood, and advise you on whether you can give blood in the future.

What is my blood type?

There are 8 main blood types, with some more common than others. These percentages give you an idea of which blood types are the most common, and which are the most rare (UK data collected in 2018). O positive: 35% A positive: 30% O negative: 13% A negative: 8% B positive: 8% B negative: 2% AB positive: 2% AB negative: 1%

If you’re not sure of your blood type, you’ll find out after your first blood donation.

You can find out more about different blood types, and why some are more in demand than others.

Which blood types are in demand?

Sometimes there will be a shortage of certain blood types – this is why regular donors will be contacted about giving blood if they have the particular blood type.

Certain blood types can also be more widely used which creates a much higher demand. Even though 8% of people in the UK have type O negative blood, this type of blood makes up 13% of blood donation requests from hospitals because anyone in need of a blood transfusion can receive the red cells from O negative donors.

If a person’s blood type is unknown in an emergency, O negative red cells will be used.

How do I give blood?

Thousands of people are already signed up to give blood – and you can too. To join the growing community of blood donors, you firstly need to register your details on the blood donation database.

Once you’ve answered a few questions to check whether you’re eligible, you’ll be asked to fill in some personal details and set up an account. The process is super quick and easy.

Through your account you can then find out where you can give blood, book an appointment, change any future appointments, update your details and view your blood donation history over the last 5 years.

Don’t worry if you can’t book an appointment straight away, as some centres get busier than others!

Are there side effects after you give blood?

Most people don’t feel any different after giving blood. It’s possible you may have some mild bruising on your arm (around the needle site). Some people can feel a bit tired or lightheaded afterwards.

‘Light bruising is completely normal and will disappear very quickly. To make sure you don’t feel dizzy after giving blood, you’ll be encouraged to have at least two drinks and a snack afterwards, and rest for at least 15 minutes before you leave,’ advises Dr Rhianna McClymont. ‘If you feel unwell, stay sitting down and let a member of staff know as soon as you can.’

Once you’re home, if you start to feel poorly in the following 2 weeks (other than a cold or cold sore) or if you believe there’s a reason your blood should not be given to a patient, call the donor helpline on 0300 123 23 23.

How to feel less anxious about giving blood

It’s completely normal to feel anxious about giving blood, especially if it’s your first time. There will be lots of helpful staff around to put you at ease as soon as you arrive at the blood donation centre – and it’s a good idea to let them know you’re feeling a bit nervous so they can offer reassurance.

One of the best ways to help your anxiety is to distract yourself. Some people bring music to listen to or a book to read.

During your blood donation, you’ll also be asked to do a simple technique called ‘applied muscle tension’. This helps to regulate your blood pressure and stop you feeling faint or unwell. It’s also another great way to distract you during your blood donation. The technique involves tensing and relaxing your muscles during the giving blood process – including clenching and unclenching your buttock muscles.

More information will be available at the blood donation centre. Ask a member of staff if you have any questions.

What to eat and drink when you give blood

Eating regularly before giving blood will help to keep your blood sugar levels stable. This is important so that you don’t feel lightheaded or dizzy afterwards.

‘It’s a good idea to have a snack before you give blood and try to eat foods rich in iron afterwards, like red meat, fish, leafy vegetables, nuts and seeds. This will help to keep you feeling fit and well during and after giving blood,’ Dr McClymont explains.

Almost half of the blood you will donate is made up of water, and so any fluids you lose during the process can lead to your blood pressure falling. To prevent this and stop you feeling faint, it’s recommended you drink lots of fluids in the days leading up to your blood donation, as well as 500ml of water right before you give blood.

Drinking lots of water after you give blood is just as important – try and bring a refillable bottle if you can to help cut down plastic waste!

Make sure you avoid any alcohol before and after the blood donation. Drinking after giving blood may affect your hydration levels and delay your blood volume returning to normal.

What to do after giving blood

Dr McClymont has shared a few things you can do to make sure you feel well immediately after giving blood, as well as for the rest of the day. They include:

  • Sit down for 15 minutes after you give blood and rest as much as you can – don’t drive if you feel faint or lightheaded

  • Keep the pressure dressing on your arm for at least half an hour after you’ve given blood, and the plaster on for at least 6 hours

  • Stay hydrated – make sure you have at least 2 drinks straight after giving blood, and avoid drinking alcohol as this can dehydrate you more

  • Eat regularly – make sure you eat a snack afterwards and eat your regular meals throughout the day to prevent you feeling dizzy

  • Avoid strenuous exercise or using the arm you gave blood from to carry anything heavy, for the rest of the day

For more advice, or if you notice any unusual side effects from your blood donation, call the helpline on 0300 123 23 23.

Can you exercise after giving blood?

‘Try to avoid exercising or lifting anything heavy on the day you give blood, especially afterwards,’ says Dr McClymont.

‘Resting your body means that you have a chance to properly recover and build up fluids that are lost during your blood donor session. It’s fine to do some light exercise like walking, as long as you stay hydrated throughout the day.’

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