A stem cell transplant is when healthy stem cells are injected into a person’s bone marrow or blood. This can replenish stem cells when a person’s bone marrow has been damaged by chemotherapy, radiation, or a disease. When the healthy cells come from bone marrow, it is also known as a bone marrow transplant.

Stem cells are unique in that they are pluripotent. This means they can change into any different type of cell. One of their primary responsibilities is tissue regeneration, which is when old or damaged tissues are replaced with new, healthy ones.

However, stem cells can be damaged during illness or treatment for an illness. Some people with cancer receive high doses of chemotherapy, radiation therapy, or both. Although this kills the cancer cells, it also kills healthy stem cells. This type of aggressive treatment is called myeloablation.

Once treatment is complete, doctors transplant new stem cells to replace the damaged ones. The goal of a transplant is that over time, the new cells will settle in the bone marrow and regenerate.

Read on to find out what stem cells are, reasons to have a transplant, types of transplants, and how they work.

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Stem cells are special cells that can transform into almost every type of cell in the human body. Their unique ability to act as different types of cells makes them incredibly important. However, they can be damaged during illness and/or treatment.

Cancer and cancer treatment can damage a person’s hematopoietic stem cells. These are stem cells that turn into blood cells. Hematopoietic stem cells often live in the bone marrow, which is a soft, spongy tissue in the center of most bones. These cells are also in a person’s blood.

When a person has a stem cell transplant, a doctor injects healthy stem cells into the bone marrow or blood. This restores the body’s ability to create new blood cells, such as red blood cells, white blood cells, and platelets.

A person usually receives a stem cell transplant because their bone marrow has been damaged, leaving it unable to produce healthy cells.

Doctors may also carry out a transplant on a person to replace blood cells that are damaged by intensive cancer treatment.

Conditions that doctors use stem cell transplants to treat include:

There are different types of stem cell transplants a person can receive. Sometimes, a person’s own stem cells are transplanted. Alternatively, donor cells or cord blood cells are used.

The different types of stem cell transplants include:


This stem cell treatment involves the transplant of a person’s own stem cells. Often, this is done before a person receives treatments such as chemotherapy or radiation, which will likely damage the body’s supply of stem cells.

A doctor will harvest the cells from the bone marrow or blood. Then, the cells are frozen. After treatment is completed, a doctor will transplant the cells back into the bone marrow.


Allogenic transplants use donor stem cells. These come from a donor who has a similar type of tissue to the recipient.

Typically, close family members make the best donors. If a person does not have an available match in their family, they can find a donor through a national registry.

There are two different types of allogenic stem cell transplant:


Syngenic stem cell transplants are a type of allogenic transplant. They can only be used when a person has an identical sibling, such as a twin or triplet, who has the exact same tissue type.

Cord blood

Cord blood stem cell transplants are also a type of allogenic transplant. In this type of transplant, donor blood from the umbilical cord or placenta is used.

This type of blood is particularly good for transplants because of its high concentration of stem cells.

Before a person can undergo a stem cell transplant, they must undergo a series of tests and examinations. These ensure they are fit to have the procedure.

The tests a may include:

  • Blood test: This checks a person’s blood cell count as well as their liver and kidney function.
  • An electrocardiogram (ECG): This simple test checks a person’s heart’s rhythm and its electrical activity.
  • An echocardiogram: Doctors use this scan to look at the heart and nearby blood vessels.
  • An x-ray, a CT scan, or both: Doctors use these scans to check the condition of organs such as the liver and lungs.
  • A biopsy: If a person has cancer, they may also need a biopsy. A doctor will remove a small sample of cells to be analyzed.

Stem cell transplants have three main phases: stem cell collection, pre-transplant treatment, and the transplant itself.

The steps for autologous and allogenic transplants are very similar. How the cells are collected is the main difference between the two.

Stem cell collection

In an allogenic transplant, a person must be matched with a donor. This can be a family member or an individual from the donor registry.

The first step is collecting cells from the donor’s blood or bone marrow. In an autologous transplant, a person’s own blood or marrow is harvested.

This process takes several days. First, a doctor gives the person an injection that increases their stem cell count. They then collect the stem cells through a vein in the arm or chest. The cells are frozen until needed.

Pre-transplant treatment

In many cases, people get stem cell transplants because they need aggressive chemotherapy or radiation. This treatment must be completed before the transplant takes place.

A doctor will administer a high dose of chemotherapy, radiation, or both. This can take 5 to 10 days.

Stem cell transplant

Once a person’s treatment is complete, they are ready to receive the new stem cells. The transplant itself, also called an infusion, takes about 30 minutes.

A catheter, or a small tube, will be inserted into the person’s chest. This is used to administer the stem cells and any other medications they may need. People may have multiple infusions.

After the transplant, a person will need to stay in hospital for a few weeks. This gives the stem cells a chance to settle into the bone marrow and begin producing new blood cells. It also gives doctors an opportunity to notice and treat any complications.

During this period, a person may:

  • feel weak
  • experience vomiting, diarrhea, and a loss of appetite
  • receive blood transfusions to increase their red blood cell count
  • be placed in a germ-free room due to their low number of infection-fighting white blood cells
  • be given fluids and/or nutrition by mouth or tube

Many people feel well enough to leave the hospital between 1 and 3 months after their transplant. Once returning home, the patient will still be at risk of infections for a period of potentially 1 or 2 years. This is because it can take time for a person’s immune system to return to full strength.

Learn more about living with a weak or compromised immune system.

Bone marrow

Many people with illnesses such as blood cancer need donated stem cells. Sometimes, they do not have a family member who is a match or is able to donate cells, so they turn to a national registry.

People who want to donate stem cells can join their local registry. Individuals located in the U.S. can contact the National Marrow Donor Program to find the nearest donor center. It is easy and quick to register, and within several days or weeks, the organization will tell the individual if they meet the eligibility criteria.

If a person needing stem cells matches with someone on the registry, they will contact them to arrange a donation.

To join the U.S. registry, people can contact:

Be the Match (formerly the National Marrow Donor Program)
Toll-free number: 1-800-MARROW-2 (1-800-627-7692)
Website: www.bethematch.org

Cord blood

People can also donate stem cells through their baby’s cord blood. In these cases, they should make arrangements as early in pregnancy as possible.

Donation of stem cells from the umbilical cord and/or placenta is safe, easy, and does not affect the birth process or baby.

The cord blood can be donated to a public bank. Alternatively, some people may choose to privately bank their cord blood for future use.

Learn more about cord blood donation and banking.

Stem cells are special cells that can transform into other types of cells.

People with certain conditions or who have undergone chemotherapy or radiation may require a stem cell transplant. They can use a person’s own stem cells harvested before treatment, or they can come from a donor or family member.

After undergoing eligibility tests, a person receives one or more infusions of stem cells. Recovery can take several months, and a person may be susceptible to infections for a year or two.

Individuals can donate stem cells by contacting the national registry.