Are there any risks involved in Stem Cell Therapy?

The risks fall into four groups: risks of the procedure (for example, pain, swelling, bruising and, rarely, infection or bleeding at an injection site, or effects of sedation); risks of the cells (most commonly a temporary fever after intravenous infusion, and rarely allergic reactions); risks related to your own health (such as heart, kidney or bleeding conditions that can make a procedure riskier); and risks of unregulated products or practices, which have caused the most serious harms reported worldwide. Large analyses of randomized trials have found that MSCs are associated with temporary fever but not with increased rates of infection, blood clots, cancer or death in controlled settings. At Stem Cell Mexico, risks are reduced through eligibility screening, a single documented cell source (Wharton's jelly MSCs from a licensed laboratory), image-guided procedures, monitoring and follow-up. Not everyone is a candidate, and treatment is declined when risks outweigh the expected benefit.

Understanding the risks clearly, without exaggerating or minimizing them, is the best way to make an informed decision. This guide explains each type of risk and how it is managed.

What the evidence shows

• A systematic review in EClinicalMedicine (Thompson and colleagues, 2020) analyzed 55 randomized controlled trials with 2,696 patients who received intravascular MSCs. The only consistent association was with temporary fever. There was no increase in acute infusion toxicity, infections, thrombotic events, malignancy or death, and no trial was stopped for safety reasons.
• A 2026 analysis in Stem Cells Translational Medicine (Hum and colleagues), focused on umbilical cord MSCs, included 42 randomized trials with 2,280 patients and found the same pattern: higher risk of temporary fever, no signals of harm for infection, thrombosis, malignancy, abnormal tissue formation or death. The authors recommended continued long-term surveillance for rare events.
• For local injections, such as in the knee or spine, randomized trials have shown similar rates of serious adverse events between MSC and control groups, with temporary local pain and swelling as the most common effects.

How likely are these risks? Putting them in perspective

It helps to think of risks in three tiers. Expected effects happen to many patients and are part of a normal recovery: soreness and swelling after injections, mild fever or tiredness after infusions, small bruises. They usually resolve within days and do not affect the final result. Uncommon effects happen to a minority of patients, such as a stronger inflammatory flare or nausea after sedation; they are uncomfortable but manageable with simple measures. Rare complications, such as infection, significant bleeding, nerve injury or a serious allergic reaction, are unlikely with proper technique and screening, but they matter because they can be serious; that is why we monitor you, explain warning signs and stay in contact. Thinking in these tiers helps you prepare for what is likely while knowing what to watch for.

1. Risks of the procedure

Injections into joints, tendons or the spine

• Common: pain, swelling, stiffness and bruising for several days; a temporary pain flare after spinal procedures.
• Rare: infection (joint infection or, in the spine, disc infection), bleeding, nerve irritation, and headache after spinal procedures.

Intravenous infusion

• Common: temporary discomfort at the IV site.
• Rare: infusion reactions, vein irritation.

Sedation

• Uncommon: nausea, drowsiness, temporary drop in blood pressure or breathing changes, monitored by trained staff.

2. Risks of the cells

• Fever: the most consistent side effect of IV MSCs, usually low-grade and lasting one to two days.
• Headache and fatigue for a day or two.
• Allergic reactions: rare, to cells or components of the preparation.
• Theoretical long-term risks, such as abnormal tissue formation or effects on tumors: not seen in controlled MSC trials, but rare events require long-term monitoring, which is why cancer within the past five years is an exclusion.

3. Risks related to your health

Some conditions make any procedure riskier:

• Heart disease, unstable blood pressure or arrhythmias.
• Kidney disease affecting fluid and electrolyte balance.
• Diabetes or immune suppression, which raise infection risk.
• Blood thinners or bleeding disorders.
• Seizures, swallowing problems or limited mobility.
• Active infection anywhere in the body.

These factors do not always prevent treatment, but they require planning, adjustments or waiting until you are stable.

Risks specific to certain conditions

Some patients face additional, condition-specific risks that are addressed in their plan. People with heart failure need careful fluid and rhythm monitoring. People with kidney disease need attention to fluids and electrolytes. People with spinal cord injury above the sixth thoracic level are at risk of autonomic dysreflexia and pressure injuries during travel. People with Parkinson's disease must keep medication schedules exact and avoid certain drug interactions, for example between MAO-B inhibitors and some pain medications such as tramadol. People with multiple sclerosis may notice a temporary worsening of symptoms with fever. These risks are discussed individually during your evaluation.

4. Risks of unregulated products and practices

The most serious harms reported in the stem cell field have occurred with unregulated products or procedures, for example:

• Injections of cells into the eye outside regulated trials, which caused severe vision loss in published cases.
• Products contaminated with bacteria because of inadequate manufacturing.
• Cells injected into the spinal cord or brain without proper oversight, with cases of abnormal growths.
• Products with unknown content marketed as "stem cells."

The U.S. National Eye Institute and the FDA have described such cases to warn patients. These risks are largely avoidable by choosing a licensed facility, a documented cell product, appropriate routes and qualified specialists.

How the risks compare with other treatments

Every treatment option carries its own risks, and it helps to compare them fairly. Daily anti-inflammatory painkillers can cause stomach bleeding, kidney problems and cardiovascular effects with long-term use. Repeated corticosteroid injections can weaken tendons and cartilage over time. Opioid painkillers carry risks of dependence and side effects. Surgery, such as joint replacement or spinal fusion, has established benefits for the right patients but also risks of infection, blood clots, anesthesia complications and a long recovery. Regenerative injections and infusions are minimally invasive and, in controlled settings, mostly cause temporary side effects, but their benefits are less certain than those of some established treatments. A good decision weighs both sides: the size and likelihood of benefit, and the type and probability of harm, for your specific condition.

Common versus rare: a practical summary

How we reduce risk

• Eligibility screening: medical questionnaire, record and imaging review, consultation and in-person evaluation.
• Exclusions: cancer within five years, active infection, pregnancy or breastfeeding, unstable conditions.
• Pre-treatment testing: complete blood count, metabolic panel, urinalysis and tumor markers.
• One documented cell source: Wharton's jelly MSCs from a COFEPRIS-licensed laboratory under GMP standards, with quality and safety testing before release.
• Image guidance and sterile technique for injections; fluoroscopy for the spine in a hospital-level setting.
• Monitoring and observation, often overnight.
• Clear instructions, warning signs and follow-up.

Risks for older adults

Many patients considering regenerative treatment are over 60. Age itself is not a reason to exclude treatment, and older adults have participated in many MSC trials, including a randomized trial in frail older adults that found no treatment-related serious adverse events. However, older patients are more likely to have heart disease, reduced kidney function, multiple medications, balance problems and slower recovery. Fasting, travel and sedation can cause dizziness or confusion. These risks are reduced by reviewing all medications, maintaining hydration as allowed, planning rest days, using assistance with mobility and including a companion when possible.

Travel-related risks

For international patients, travel adds its own considerations: long flights and car rides increase the risk of blood clots, especially after leg or spine procedures; dehydration and fatigue can worsen dizziness; and changes in routine can affect medication schedules. Staying hydrated, moving regularly during travel, scheduling return flights after your discharge check-up and carrying all medications in your hand luggage reduce these risks.

Risks you can help reduce

• Follow pre-treatment instructions about medications, supplements, alcohol and fasting.
• Disclose all medications, supplements and medical conditions.
• Rest and follow the recovery plan; avoid overloading treated areas.
• Keep follow-up calls and report unusual symptoms early.

The risk of not achieving the result you expect

A risk that is easy to overlook is that the treatment may not help as much as you hope. Evidence of benefit is most mature for conditions such as knee osteoarthritis and degenerative disc disease. We discuss realistic goals before treatment so expectations are clear.

Regulatory context

In the United States, only one MSC product has been approved by the FDA, for a pediatric transplant complication. In Mexico, establishments that handle stem cells operate under sanitary licenses from COFEPRIS. Ask any provider for documentation of the product and facility.

How informed consent works

Before your procedure, you receive an informed consent document that explains the treatment, its expected benefits, its risks, alternatives and the evidence for your condition. You can ask questions, take time to read it and decline at any point before the procedure. Signing consent means you understand the information, not that you give up your right to ask for help if something goes wrong.

Signs to report after treatment

Contact the team or seek urgent care for high or persistent fever, increasing redness, heat or swelling at an injection site, worsening pain after the first days, chest pain, shortness of breath, new weakness or numbness, or severe headache.

Questions to ask during your evaluation

• What are the specific risks of my procedure and route?
• Do my health conditions or medications increase any risk?
• How are cells tested before release?
• What monitoring will I have, and how do I reach the team after I go home?
• What results are realistic for my condition?

Bottom line

Stem cell therapy has risks, but with documented cells, appropriate procedures and careful screening, most side effects are temporary and serious complications are rare. The most serious harms in the field have come from unregulated products and practices. A medical evaluation can help determine whether this type of regenerative treatment is appropriate and safe for your condition, goals and medical history.