Blood is essential for supporting life. It transports oxygen and nutrients and helps regulate functions such as body temperature. A blood transfusion provides healthy blood when a person’s body has difficulty producing it.

Blood transfusion is a common procedure. According to the American Red Cross, someone in the United States needs blood every 2 seconds. Meanwhile, nearly 21 million transfusions of blood elements, such as red blood cells, platelets, or plasma, take place each year in the U.S. alone.

Here, we look at how long a transfusion takes, when it starts working, and what the process involves.

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The amount of time it takes to receive a blood transfusion varies.

It depends on how much blood and which blood products the person needs. According to the National Heart, Blood, and Lung Institute, a blood transfusion typically takes 1–4 hours.

How long does a transfusion for anemia take?

People with anemia may need transfusions of red blood cells. These take longer than transfusions of plasma or platelets. The typical duration of a red blood cell transfusion is 4 hours.

The table below shows how long different transfusions may take, based on information from the Joint United Kingdom Blood Transfusion and Tissue Transplantation Services Professional Advisory Committee. But these times can vary, based on several factors specific to each person.

Type of transfusionTiming
Red cellsFor many people, this takes 90–120 minutes per unit. But for a severe hemorrhage, it may be possible and necessary to give each unit in 5–10 minutes.
PlateletsThis transfusion usually takes 30–60 minutes per unit.
Fresh frozen plasmaThe rate is usually 10–20 milliliters per hour.

Learn more about blood transfusions and anemia.

Are there any ways to speed it up?

Barring emergency situations, a healthcare professional aims to administer a transfusion at a pace that suits the person.

The speed of a blood transfusion depends on:

  • the type of transfusion
  • the person’s age
  • their weight
  • their overall health
  • whether they have had complications in the past
  • whether they have any type of heart disease

When a person notices a difference after a transfusion varies between individuals.

This can depend on the reason for the transfusion. One study from 2009 showed that people with cancer and anemia reported a significant increase in their sense of well-being and had improved hemoglobin counts immediately after receiving a transfusion of red blood cells.

However, if the person has lost blood due to a traumatic injury, the benefits are likely to take longer to show. It will depend on the amount of blood lost and any other health issues. In this case, the person may need more than one transfusion, as well.

The duration of the benefits depends on the reason for the transfusion. We explore some specifics below.

Surgery, trauma, and accidents

When a person needs blood due to a traumatic injury or during surgery, the benefits tend to last. This is because the transfusion replaces lost blood.

Once the person’s condition is stable, and they have lost no more blood, they are unlikely to need another transfusion.

Chronic diseases, cancer, and anemia

If a person has a long-term illness, they will likely need further transfusions. The length of time before the next transfusion depends on the health issue and factors specific to the person.

Some people with myelodysplastic syndrome, a bone marrow disorder that can lead to a form of anemia, for example, may need a transfusion every 2 weeks, while others need them every few months.

Overall, once a person starts having transfusions, the intervals between tend to become shorter over time. The person’s red blood cell count can indicate when a transfusion is appropriate, but there is no specific threshold or number, and the doctor will make the decision with the person.

One study found that people with cancer and anemia experienced significant improvements from transfusions and that the improvements lasted for about 15 days.

How many transfusions can a person have?

A person might need a transfusion if they:

  • lose blood due to an injury or during surgery or childbirth
  • have a health condition, such as sickle cell disease, that affects how their blood cells work
  • have cancer or receive cancer treatment, such as chemotherapy, which can affect blood cells

The circulatory system of the average, healthy adult contains about 1.2 to 1.5 gallons of blood. This is 10 units. Blood makes up around 10% of a person’s body weight.

If a person loses 15–30% of their blood, it starts to affect their heart rate. If they lose 30–40%, it may also affect their mental state. If they lose 40% or more, their blood pressure falls dramatically, and their heart rate increases significantly. They may lose consciousness as the oxygen supply to their brain falls.

Learn more about blood volume here.

Not all blood transfusions are the same. The difference lies in what component of blood a person receives. The most common types are:

  • whole blood transfusions, which contain all the components of blood
  • plasma transfusions
  • platelet transfusions
  • red blood cell transfusions

Whole blood transfusions are less common. Separating blood into its different parts makes it possible for more people to benefit from a single unit of blood.

Are there different times for different types of blood transfusion?

According to the American Cancer Society, each unit of red blood cells takes around 2 hours to transfuse. Transfusions usually start slowly and should take no more than 4 hours.

Transfusions of plasma or platelets take less time. The United Kingdom’s National Health Service reports that it takes 30–60 minutes to transfuse 1 unit of plasma or platelets, compared with 2–3 hours for one unit of red blood cells.

We give more information from a different source in the table above.

Blood transfusions take place in a doctor’s office or hospital. First, the doctor takes a blood sample and runs a complete blood count test to confirm what sort of transfusion the person needs.

Using a needle, the doctor inserts an intravenous (IV) line into a blood vessel. Once the line is in place, they remove the needle and allow the new blood or blood products to flow into the person’s vein.

If the person has anemia due to a chronic illness, such as kidney disease or cancer, they may already have a device that provides long-term or permanent access to a vein. In this case, the person does not need a new IV insertion every time they have a transfusion.

The doctor will monitor closely for signs of an adverse reaction, especially during the first 15 minutes of the transfusion. However, a reaction can appear up to several weeks afterward.

Some signs of an adverse reaction include:

  • hives or other signs of an allergic reaction
  • fever or chills
  • loin, chest, or back pain
  • pain around the transfusion site
  • distress
  • changes in heart rhythm
  • jaundice
  • dark or red urine
  • nausea, vomiting, or both
  • difficulty breathing
  • faintness or weakness

The doctor will need to judge whether the symptoms stem from the transfusion or a worsening of the person’s condition.

When the transfusion is complete, the doctor removes the IV line. The person may notice bruising or discomfort for a few days at the site of the IV.

Depending on the reason for the transfusion, doctors may carry out post-transfusion blood tests to evaluate the body’s response.

People usually do not need to change their routine or diet before or after a blood transfusion.

A person may need a blood transfusion if they lose blood due to an injury, surgery, or childbirth. People may also need transfusions if they have a medical condition that prevents their blood from functioning effectively.

A transfusion can take 1–4 hours. Some people notice improvement right away. For others, the benefits may take time to appear. How long this takes, and how long the improvement lasts depends on the person and their reason for needing a transfusion.