A stem cell infusion is a procedure in which stem cells are delivered into the bloodstream through an intravenous (IV) line, similar to a blood transfusion. The cells travel through the body and, in the case of bone marrow transplants, settle into the bone marrow where they begin producing new blood cells. The procedure itself typically takes 20 minutes to an hour, but it sits at the center of a much longer treatment process that can span weeks or months.
How Stem Cell Infusions Work
The basic idea is straightforward: healthy stem cells enter your bloodstream and migrate to where they’re needed. But the biology behind this migration is surprisingly precise. Damaged or diseased tissue releases chemical signals called chemokines, which act like a trail of breadcrumbs. Stem cells have receptors on their surface that detect these signals and follow the concentration gradient toward the injury site. Once they arrive, they latch onto blood vessel walls and push through into the surrounding tissue.
The most well-studied version of this navigation system involves a signal molecule called SDF-1, which injured tissues release in high concentrations. Stem cells carrying the matching receptor lock onto this signal and home in on the damage. This is a multi-step process: the cells first travel through the bloodstream, then adhere to blood vessel walls near the injury, and finally cross through the vessel lining into the tissue itself.
Types of Stem Cells Used
Not all stem cell infusions use the same type of cell. The two major categories are hematopoietic stem cells and mesenchymal stem cells, and they serve very different purposes.
Hematopoietic stem cells are blood-forming cells. They were among the first stem cell types used in medicine, primarily to rebuild the blood and immune system after chemotherapy or radiation has destroyed a patient’s bone marrow. These cells give rise to red blood cells, white blood cells, and platelets. For patients with blood cancers like leukemia or multiple myeloma, hematopoietic stem cell transplant remains one of the most established treatments available.
Mesenchymal stem cells are a different population entirely. They can develop into bone, cartilage, muscle, and fat cells, but they do not produce blood cells. These cells can be harvested from many sources: bone marrow, fat tissue, umbilical cord blood, placenta, and even the dental pulp of baby teeth. Mesenchymal stem cells have been tested in clinical trials for osteoarthritis, Crohn’s disease, multiple sclerosis, lupus, graft-versus-host disease, and sepsis, though most of these uses remain investigational.
Your Own Cells vs. a Donor’s
Stem cell infusions fall into two broad categories depending on where the cells come from. An autologous transplant uses your own stem cells, collected and stored before treatment. An allogeneic transplant uses cells from a matched donor.
Autologous transplants are simpler in many ways. There’s no need to find a donor match, no risk of your body rejecting the graft, and no need for immunosuppressive drugs afterward. Immune recovery tends to be faster, and treatment-related mortality stays below 5% in most studies. Even elderly patients generally tolerate the procedure. The tradeoff is that your own cells could be contaminated with residual cancer cells, and there’s no immune attack against remaining cancer, so relapse rates tend to be higher.
Allogeneic transplants offer a cleaner graft with no tumor contamination, plus a powerful benefit: donor immune cells can recognize and attack remaining cancer cells, an effect known as graft-versus-malignancy. Relapse rates are generally lower. But the complications can be severe. The donor’s immune cells may also attack your healthy tissues, a condition called graft-versus-host disease. Immune recovery takes longer, infections are more common, and treatment-related mortality is significantly higher, especially when the donor is not a perfectly matched sibling.
What the Procedure Looks Like
The infusion itself is the simplest part of the process. You sit or lie in a treatment chair while stem cells flow through an IV line into your bloodstream, a process that takes roughly 20 minutes to an hour depending on the volume of cells. Afterward, you stay for about two hours of observation in case of a delayed reaction.
The harder part comes before the infusion. For hematopoietic stem cell transplants, you first undergo conditioning therapy, a combination of chemotherapy, radiation, or both. This serves three purposes: destroying the disease, clearing space in the bone marrow for the new cells to take root, and suppressing your immune system enough that it won’t reject the incoming cells. Conditioning regimens range from myeloablative (high-dose, which wipes out the existing marrow entirely) to reduced-intensity or non-myeloablative approaches that are less toxic but still create room for engraftment.
For blood cancer patients, the dosing of infused cells matters. In multiple myeloma, research has identified a sweet spot: receiving more than 2.5 million stem cells per kilogram of body weight is associated with better overall survival compared to lower doses. But higher isn’t always better. Doses above 8 million cells per kilogram have actually been linked to shorter survival, suggesting a ceiling effect.
Risks and Side Effects
Most clinical studies report that stem cell infusions, particularly mesenchymal stem cell therapies, are safe with only minor side effects. Fever is the most common reaction, appearing in roughly 10 to 20% of patients across various conditions, though rates as high as 85% have been reported in progressive multiple sclerosis patients receiving their own bone marrow-derived cells. Fever sometimes results from a reaction to the preservative solution rather than the cells themselves. Joint injections of stem cells can cause mild swelling and increased pain at the injection site for 48 to 72 hours.
More serious complications exist. Clinical trials have identified blood clots and tissue scarring (fibrosis) as the most common major adverse events from mesenchymal stem cell therapy. Cases of blood clots in the lungs and kidneys have been documented in kidney transplant patients following infusion, and one patient with chronic kidney disease developed scarring and tissue damage in the kidneys after receiving fat-derived stem cells. For allogeneic hematopoietic transplants, graft-versus-host disease remains a significant risk that can affect the skin, liver, and digestive tract.
What’s Actually Approved
The only stem cell infusion therapy routinely approved by the FDA is hematopoietic stem cell transplantation for cancers and disorders affecting the blood and immune system. That’s it. Despite hundreds of clinical trials investigating stem cells for everything from arthritis to heart failure, no other stem cell infusion has cleared the FDA’s approval process as a standard treatment.
This matters because a growing number of clinics market stem cell infusions for conditions that have no approved stem cell therapy. The FDA has taken aggressive action against clinics selling unapproved stem cell products, including obtaining a permanent court injunction against a Florida clinic that manufactured fat-derived stem cell products without FDA authorization. Over the course of one year alone, the agency sent 46 regulatory letters to manufacturers and healthcare professionals offering unproven stem cell treatments. In its enforcement actions, the FDA has pointed to real patient harms from unregulated clinics, including blindness, serious infections, and death.
If you encounter a clinic offering stem cell infusions for conditions outside of blood cancers or immune disorders, and the treatment isn’t part of a registered clinical trial, that’s a significant red flag. Legitimate stem cell research is advancing rapidly, but the gap between promising lab results and proven clinical treatments remains wide for most conditions.