How Blood Donation Works: Each Step and How Long It Takes

What are the steps of giving blood?

1. Registration: you show your ID and read some short information.
2. Health questions and a quick check-up: you answer questions about your health in private, and the team checks your temperature, blood pressure, pulse and hemoglobin.
3. The donation: you sit comfortably while about half a litre of blood is drawn; the draw itself takes 8 to 10 minutes.
4. Rest: you have a snack and a drink for 10 to 15 minutes, then go back to your day.
5. Testing: your blood is tested in the lab and then sent to a patient who needs it.

According to the American Red Cross, the whole visit takes about an hour.

How should you prepare?

• Get a good night’s sleep the night before.
• Have a healthy meal before your appointment and avoid fatty food.
• Drink about half a litre of extra water before your appointment.
• Eat iron-rich food in the days before.
• Bring your ID and a list of your medicines, and wear sleeves you can roll up above the elbow.
• If you are giving platelets, do not take aspirin for 2 days before your appointment.

And check the basic requirements with Can I donate blood today?.

How can you avoid feeling dizzy?

The American Red Cross recommends a simple muscle-tensing exercise: cross your legs and squeeze your thighs or knees together, tighten your stomach muscles and flex your feet. Hold for 5 seconds, relax for 5 seconds, and repeat several times before the needle goes in, during the donation if you feel lightheaded, before the needle comes out and before you stand up.

The Red Cross says this exercise reduces the chance of fainting or feeling faint by up to 83%.

What happens to your blood after you give it?

Your blood bag and test tubes get the same code, and most whole blood donations are spun in centrifuges to separate them into red cells, platelets and plasma. That is how one donation can help more than one patient.

Every unit is tested in the lab before it is given to a patient.

What should you do afterwards?

Rest, drink extra fluids, avoid hard exercise for the rest of the day and eat iron-rich food. Details in the guide what to eat and do after giving blood.

Frequently asked questions

Sources

This guide is based on the following published sources:

1. First Time Blood Donors Guide American Red Cross
2. Tips For A Successful Blood Donation American Red Cross
3. What Happens to Donated Blood American Red Cross

Content and links last reviewed: 17 October 2026. How we write the tools

This tool gives general guidance based on published rules, which differ by country and change over time. It does not replace a medical assessment. The doctor at the donation centre always makes the final decision. In an emergency, call your local emergency number.