MMP-9 (MATRIX METALLOPROTEINASE-9) EDUCATION
Updated: 6 days ago
MMP-9 is one of the lab markers that comes up a lot with mold and CIRS. I was taught that a high MMP-9 doesn't have to mean mold. Other things can be at play, so keep that in mind. Here is what MMP-9 is, why it can be high with mold, Lyme and inflammation, and what the doctors I trust say a result can and can't tell you.
Short on time or energy? A quick-view graphic with the key points is at the bottom of this post.
New to mold? Start with my Mold Illness Education post:
Looking for things that may help? See my Mold - Possible Solutions post:
WHAT MMP-9 IS
- MMP-9 is short for matrix metalloproteinase-9. It is also called gelatinase B.
- It is an enzyme that breaks down proteins in the extracellular matrix, the support structure that sits between our cells.
- In the right amount, enzymes like this help with wound healing and repair.
- Inflammatory cytokines, such as TNF-alpha and IL-1 beta, can switch on more MMP-9. Learn more about cytokines here:
- Researchers think too much MMP-9 may play a part in inflammation and a leakier blood-brain barrier, and it is being studied in depression too. Learn more about the blood-brain barrier here:
- Dr. Ritchie Shoemaker, who developed the CIRS model, explains that MMP-9 helps move inflammatory substances out of the blood and into tissues like the brain, lungs, muscles, nerves and joints.
MMP-9 IN MOLD AND CIRS
- MMP-9 was one of the first inflammation markers Dr. Shoemaker used for CIRS, and it was part of his testing by 2003. Learn more about CIRS here:
- Dr. Jill Carnahan still uses MMP-9 as part of the CIRS blood panel for her mold patients (2026), along with TGF-beta 1, C4a, VEGF, MSH and VIP. She pairs it with a urine mycotoxin test, an HLA-DR gene test and a visual contrast test.
- Dr. Carnahan also lists MMP-9 as one of the markers seen more often when mold is what set off mast cell activation (MCAS).
- In a 2025 lab study, the mold toxin ochratoxin A made human brain immune cells (microglia) release more MMP-9. This was a lab study, not a study in people.
- Dr. Jill Crista's mold questionnaire counts a CIRS diagnosis or positive Shoemaker (CIRS) tests as one clue among many, along with symptoms and past exposure to water-damaged buildings.
MMP-9 IN LYME AND INFLAMMATION
- Lab research suggests the Lyme bacteria can raise MMP-9 too. In a 2026 University of Iowa lab study, joint lining tissue from people having joint replacement surgery made more MMP-9 after it was exposed to the Lyme bacteria.
- In a 2023 lab model of the human blood-brain barrier, infection with a European Lyme species turned up the MMP-9 gene.
- Older research points the same way. A 2003 study found MMP-9 about 1,900% higher in fluid from the Lyme rash than in nearby normal skin. A 2000 study found MMP-9 activity in the spinal fluid of 26 of 31 people with Lyme affecting the nervous system, and in none of 20 people with other, non-inflammatory nerve conditions. A 2009 mouse study found mice without MMP-9 had much less Lyme arthritis.
- Dr. Neil Nathan finds MMP-9 and the other CIRS markers can be high with Lyme, Bartonella, other infections and some viruses, not only with mold.
- In his 2024 report on three patients with chronic Lyme, Dr. Richard Horowitz checked mold with urine mycotoxin tests. For one patient, his first round of labs also included MMP-9, along with other inflammation markers like C3a and C4a and a mold antibody test. His MSIDS model counts mold as one of many possible sources of inflammation in chronic Lyme.
- Global Lyme Alliance explains that mold and Lyme both cause inflammation, and having both can push the immune response into overdrive.
- Mast cells are part of the picture too. A 2025 review lists MMP-9 among the substances mast cells release. Learn more about mast cells here:
TESTING
- MMP-9 is a blood test. Your doctor's lab will list its own normal range.
- It is not a common test, so not every lab runs it. Dr. Carnahan stresses that the sample has to be handled carefully, or the result can be off.
- The type of blood sample matters. A 2025 lab methods paper explains that MMP-9 can read falsely higher in serum than in plasma samples.
- More on the other mold and Lyme tests is in my Lab Tests post:
DOCTORS DON'T ALL AGREE
Every doctor has their own testing preferences, and that's okay. Here is how the mold doctors I trust see it.
- Dr. Shoemaker relies on blood markers like MMP-9 as part of how he defines CIRS. He questions how much urine mycotoxin tests can prove.
- Dr. Nathan used MMP-9 and the other CIRS markers on every patient in his early years. Now he relies on the urine mycotoxin test to show which mold toxins are in the body, because the blood markers can't pinpoint mold.
- Dr. Carnahan uses both the CIRS blood panel and the urine mycotoxin test, along with home testing to find the source.
- Dr. Marty Ross agrees that CIRS markers are indirect tests and that an abnormal result could come from chronic tick-borne infections.
WHAT A HIGH MMP-9 CAN AND CAN'T TELL YOU
- It is a clue that there is inflammation, not proof of what is causing it.
- Mold, Lyme, co-infections, other infections and mast cell activation can all be part of the picture, and more than one can be at play at the same time.
- Look at the whole picture with a mold-literate doctor:
MY EXPERIENCE
- I've dealt with high MMP-9 results myself and treated accordingly, with my doctor guiding me.
BEFORE YOU START
- Go over every lab result with your doctor before making any changes to your treatment.
RELATED POSTS
MOLD DIRECTORY
CIRS (CHRONIC INFLAMMATORY RESPONSE SYNDROME) AND RELATED MOLD ISSUES
NEUROQUANT MRI
SOURCES
Dr. Neil Nathan and Dr. Ritchie Shoemaker, Better Health Guy podcast, episode 238 (2026)
Dr. Neil Nathan, interview with Dr. Mark Hyman (2026)
Dr. Jill Carnahan, Clinical Pearls for Mold and Mycotoxin Illness (2026)
Dr. Jill Carnahan, Mold, Mycotoxins, and Your Immune System (2026)
Dr. Jill Carnahan, Can MCAS Really Be Triggered by Toxic Mold? (2023, updated 2024)
Dr. Jill Crista, Mold Questionnaire (no date shown)
Dr. Ritchie Shoemaker, Surviving Mold, Lab Tests (no date shown)
Dr. Marty Ross, Mold Toxin Illness in Tick-Borne Diseases (2026)
Horowitz and others, Dapsone combination therapy, 3 cases, Microorganisms (2024)
Global Lyme Alliance, How Are Mold Illness and Lyme Disease Related? (2023)
Li and others, MMP-9 review, Frontiers in Neurology (2022)
Mulford and others, Lyme bacteria and human joint lining, Frontiers in Immunology (2026)
Kulkarni and others, Blood-brain barrier model and Borrelia, Frontiers in Cellular and Infection Microbiology (2023)
Tsilioni and others, Ochratoxin A and human microglia, International Journal of Molecular Sciences (2025)
Tziastoudi and others, Mast cell mediators review, International Journal of Molecular Sciences (2025)
Conde-Tella and others, Measuring MMP-9 in blood samples, Methods in Molecular Biology (2025)
Zhao and others, MMP-9 in the Lyme rash, Journal of Infectious Diseases (2003, older source, still worth reading)
Kirchner and others, MMP-9 in spinal fluid in neuroborreliosis, J Neurol Neurosurg Psychiatry (2000, older source, still worth reading)
Heilpern and others, MMP-9 and Lyme arthritis in mice, Infection and Immunity (2009, older source, still worth reading)
Disclaimer: Rise Above Lyme makes no claims about any possible benefit of using any product mentioned within this site. Always consult with your doctor before adding anything. The information shared is based on personal experience, years of accumulated researched resources from Lyme Literate doctors and polls conducted within Lyme groups from actual patient experience using these solution ideas.
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