GLP-1 Medications and Mast Cell Activation Syndrome (MCAS)
What is MCAS?
Mast Cell Activation Syndrome (MCAS) is a condition in which mast cells — a type of immune cell found throughout your body — become overactive and release too many chemical signals. This can cause a wide range of symptoms, including flushing, itching, hives, abdominal pain, diarrhea, brain fog, fatigue, and in some cases, severe allergic-type reactions.
What are GLP-1 medications?
GLP-1 receptor agonists (sometimes called “GLP-1 medications”) are a class of drugs originally developed for type 2 diabetes and weight management. Common brand names include Ozempic, Wegovy, Mounjaro, and Zepbound. These medications work by mimicking a natural hormone in your body called GLP-1.
Why might GLP-1 medications help with MCAS?
Researchers have found that mast cells have receptors for GLP-1, meaning these medications may directly interact with the cells that cause MCAS symptoms. GLP-1 medications are also known to have broad anti-inflammatory effects throughout the body, which may help calm the overactive immune response seen in MCAS.
What does the research show?
– A recent study by Dr. Lawrence Afrin and colleagues looked at 47 patients with MCAS who had not responded well to standard treatments. About 89% of those patients experienced some clinical benefit from GLP-1 medications.
– Important limitations of this study: This was a single-center study with no control group (meaning there was no comparison to a placebo or other treatment). Without a control group, it is difficult to know how much of the improvement was due to the medication itself versus other factors such as the placebo effect, natural fluctuations in symptoms, or other treatments patients may have been using at the same time. The results may also reflect bias, since both the doctors and patients knew the treatment being given. Larger, well-designed clinical trials with control groups are needed before we can say with confidence how well these medications work for MCAS.
Important safety information
– GLP-1 medications are not yet approved by the FDA for treating MCAS. Using them for this purpose is considered “off-label.”
– Common side effects of GLP-1 medications include nausea, vomiting, diarrhea, and decreased appetite. These side effects often improve over time, especially with slow dose increases.
– There is some evidence that GLP-1 medications may be associated with a small increased risk of allergic reactions. Because people with mast cell conditions may already be at higher risk for severe allergic reactions, your doctor may recommend starting at a very low dose and increasing slowly.
– Always have your epinephrine auto-injector (EpiPen) available when starting any new medication.
What should you do?
– Talk to your doctor before starting or stopping any medication. Your doctor can help you decide whether a GLP-1 medication might be appropriate for your situation.
– Do not stop your current MCAS medications without discussing it with your care team.
– Report any new or worsening symptoms promptly after starting a new medication.
The bottom line
GLP-1 medications are a promising new area of research for MCAS, but they are not yet a proven or standard treatment. The current evidence is very early and has significant limitations. If you are interested in exploring this option, have an open conversation with your doctor about the potential benefits and risks based on your individual health needs.
Key methodological limitations of the Afrin et al. case series include its single-center design, lack of a control group, potential for placebo effect, and risk of bias from the unblinded design.[1] These are important points for patients to understand so they can have realistic expectations and make informed decisions with their care team.
References
- Utility of Glucagon-Like-Peptide-1-Receptor Agonists in Mast Cell Activation Syndrome. Afrin LB, Weinstock LB, Dempsey TT, et al. The American Journal of the Medical Sciences. 2025;:S0002-9629(25)01106-1. doi:10.1016/j.amjms.2025.07.006.
