Cell Count, Viability, and Documentation: What Patients Should Demand Before a Procedure

Ask for a written report before the injection, and know its limits. A same-day bone marrow report can show how many nucleated cells are in the concentrate, what share passed a viability test, when and how that was measured, and by whom. It cannot reliably say how many are stem cells, and it cannot show the injection will work.

What can a same-day report show, and what can it not?

Item	Can it be on a same-day report?	What it tells you	What it does not tell you
Total nucleated or mononuclear cell count	Yes	How many cells with a nucleus are in the concentrate, per milliliter and in total	How many are stem cells; see below
Viability percentage	Yes	The share of cells that passed a live/dead test at the time of testing	Whether those cells will do anything useful in your joint
An estimate of stem cells by marker testing (flow cytometry)	Only if the clinic has the equipment	An estimate based on proteins on the cell surface	Anything about benefit; ask which markers were used
Colony count (CFU-F), the laboratory test for cells that can multiply	No	In one human study, colonies were counted at 10 and 20 days of culture (Knee Surg Sports Traumatol Arthrosc, 2022), so a colony result is not available on procedure day
Date, time, method and the name of the person who ran the test	Yes	Whether the numbers describe what went into your syringe

Sources for the table: Knee Surg Sports Traumatol Arthrosc, 2022.

Why is a cell count not a stem cell count?

Bone marrow concentrate is mostly other cells. A 2022 study describes marrow stem cells as “extremely low, ranging from 1/10,000 to 1/100,000 of total nucleated cells” (Knee Surg Sports Traumatol Arthrosc, above), and a 2017 review puts the figure at “only 0.001% of nucleated cells” in marrow aspirate (<a href="https://www.sicot-j.org/articles/sicotj/fullhtml/2017/01/sicotj160095/sicotj160095.html”>SICOT-J, 2017). Spinning the marrow concentrates all of these cells together.

A high total count does not guarantee more stem cells either. In a study of marrow concentrate from horses, the authors found “none, or a very weak correlation” between nucleated cell count, colony count and stem cell count, and concluded that “more advanced laboratory techniques such as flow cytometry should be used” until a simpler method exists (J Cartilage Joint Preservation, 2021). That was an animal study, but it is the reason to ask how any “stem cell number” on your report was produced.

Your own count will also depend on you. The 2022 study found more mononuclear cells per milliliter in younger patients than older ones, and more from the pelvis than from the shin bone (above).

Is there a right dose or a minimum viability?

The trial evidence does not settle a dose. The 2025 Cochrane review of stem cell injections for knee arthritis rated its evidence low certainty in part because the source, preparation and dose of cells differed between trials (<a href="https://www.cochrane.org/evidence/CD013342what-are-benefits-and-risks-stem-cell-injections-knee-osteoarthritis”>Cochrane). If a clinic says it has a “target dose,” ask where the number comes from and whether it was set for this kind of product.

For a clinic that relies on the same surgical procedure exception, the FDA’s tissue rules do not apply at all: FDA guidance says an establishment that qualifies is “excepted from the requirements under Part 1271” (FDA guidance, November 2017). What the report contains, and what the clinic counts as acceptable, is the clinic’s own standard, so ask what its minimum is and what it does when a sample falls short.

A viability number also measures less than it sounds like. The common dye test counts cells as dead when their membranes are damaged. Researchers writing about laboratory cell cultures note that cells can lose normal function before their membranes fail, and call the dye method “a gross overestimation of culture viability as defined by the ability of cells to recover and divide” (BioProcess International, 2019).

Where are the cells processed, and why does it matter?

Where	What it means for you
In the procedure room, with a closed kit and a centrifuge	Same clinic, same visit. Whether the processing stays within the legal exception is a question for a lawyer
In a laboratory inside the same clinic	Same as above. Having a lab on site is a business choice; what matters is the paperwork it can give you
Shipped to a separate laboratory and sent back	FDA guidance says the exception "generally applies only to those establishments that both remove and implant the autologous HCT/P at the same establishment," and that shipping "raises safety concerns, such as contamination and cross-contamination, beyond those typically associated with surgery" (FDA guidance, above)
Grown in culture for days or weeks	The same guidance lists "cell isolation, cell expansion, cell activation, or enzymatic digestion" among steps that generally take a product outside the exception (above). A product grown in culture belongs in an FDA-authorized trial

How these rules fit together, and what the other federal pathway requires, is in our summary of the rules a clinic must meet to offer cells outside a trial.

The procedure day, step by step

Consent. You review and sign the consent form before anything is drawn. The guide to consent forms lists what it should say.
Harvest. Bone marrow is drawn with a needle from the back of the hip bone after numbing medicine. The risks of that step are in the stem cell overview’s risk section.
Processing. The marrow is spun to concentrate the cells, by one of the routes in the table above.
Testing and review. The count and viability test are run, and the physician should look at the results before injecting.
Injection. The concentrate is injected, possibly under imaging; the page on needle guidance and its limits explains what imaging does and does not prove.
Aftercare. You leave with written instructions. The warning signs that mean you should call apply after this injection as after any other.

What should you ask for, and when?

Ask at the consultation, not on the day:

“Will I get a written report of what was injected, before the injection?”
“What will it list: total cell count, viability, and any stem cell estimate? By which method?”
“What is your minimum for proceeding, where does that number come from, and what happens if my sample is below it?” Ask whether you pay for a procedure that is stopped.
“Where will my cells be processed, and by whom?”
“Will the report go in my medical record, and will I get a copy?” If it is part of your record, HIPAA gives you a right to a copy (HHS).

The report is one part of judging a clinic; our clinic checklist and first-visit questions cover the rest.

What if there is no report, or it looks wrong?

A clinic that will not describe its report, or says it has none, is asking you to pay for a product you cannot check. A report with no date, time or method cannot be matched to your sample. A “stem cell count” with no stated method is not something you can interpret. Any of these is a reason to wait, and so are the other signs that a clinic is selling beyond its evidence. Price questions, including whether processing is billed separately, belong with costs and getting a coverage answer.

Does a good report mean the treatment works?

A perfect report tells you what went into the syringe. It does not tell you the treatment works. The 2017 review links the number of these marrow cells to bone healing in fractures, not to pain relief in arthritic joints, and the Cochrane review found small, low-certainty benefits for stem cell injections in the knee. A clinic can hand you a detailed report for a treatment that does not help. The report protects you from paying for an unknown product; it does not answer whether to have the procedure.

What should you demand?

A written report, before the injection, with the cell count, viability, method, time and who ran it, plus a plain answer about what the numbers can and cannot mean. Without it, you cannot check what you are paying for. With it, the question that remains is the evidence for your condition, which no report can answer.

This page is general information, not medical or legal advice.