I have been living with mast cell activation syndrome (MCAS) long enough to know how exhausting it is. As a former food writer, I’m exhausted trying to manage the sliver of foods I can tolerate well. I’m exhausted trying to live with a condition that consistently surprises me with new triggers and pain. And I’m exhausted trying to determine what research exists to support the Internet’s advice of the day, and whether it’s true or not. Part of why I wrote a 20,000-word page about MCAS is because I know well what it is like to not have reliable, accessible information, and I wanted to share my personal experiences and research notes in case they supported someone else.
The thinking applied to my starting to trial a GLP-1 medication to see if it helped move the needle on my reactivity and pain. With an ongoing spinal CSF leak, my pain levels impact me so severely that I have to treat every ‘standing up’ moment as an opportunity cost. Could taking a smaller dose of a GLP-1 medication really help me, despite all my comorbidities? I was skeptical after I saw a few anecdotes on Facebook groups or Reddit, but they began to pile up. At the same time, research emerged that mentioned the use of this class of medications for conditions outside of diabetes or obesity.
I gave it a try at a very, very low dose. Months later, I continue to use a microdose. It was so supportive of my needs that I felt compelled to share what I experienced on my social media, and was asked to write a longer post. I’m not writing this because I think my experience is universal, or because I want to position a medication as a cure for something that is stubbornly, frustratingly complex. For starters, there is a broad range of medication experience with MCAS, especially in whether a patient tolerates a medication or not. Secondly, as the data show with other conditions (and as my inbox also confirms), the GLP-1 medications help when taking them. They are not a cure. Patients revert back to their former baseline(s) after stopping them, whether it’s gaining weight back, liver labs reverting to abnormal ranges, intracranial pressure going back up, or otherwise. As with the antihistamines and other mast cell stabilizers for MCAS, patients are unlikely to be ‘fixed’ once stopping them.
Below I share my personal account of what my n=1 looks like, and an overview of what the science currently says about why GLP-1 medications may be particularly relevant for those of us with mast cell-driven, inflammatory conditions. I’ll be referring to this class of medication as GLP-1RAs throughout, shorthand for GLP-1 receptor agonists. As always, nothing here is medical advice — please work with a knowledgeable clinician before considering any new treatment.
My trial of tirzepatide for my MCAS symptoms
The GLP-1 medication I have been using is tirzepatide, also branded as Mounjaro. As noted above, I have been using it at a dose far below what you’ll see in any clinical trial or pharmacy packaging, referred to as a ‘microdose’. The standard starting dose for this medication is 2.5 mg; I am using 250 µg (that’s micrograms, equivalent to 0.25 mg, a fraction of that 2.5 mg starting dose). At my small dose, there is no branded version available since the pens that dispense the medication aren’t built with dosing that small. Compounded tirzepatide is what makes this possible, or buying directly from research labs and reconstituting at home. Doctors warn that purchasing from compounding pharmacies, and especially from unvetted research laboratories that sell products labelled as ‘not for human use’, is a risky move: public COAs (certificates of analysis) can be faked, and you don’t fully know if what you’re getting is what you bought because there are different safety measures in place for branded medication.
You will find plenty of debate online about whether microdoses do anything at all. I can only speak to my own experience: with MCAS and its many comorbidities, I have always been medication sensitive, and that sensitivity seems, in this case, to be working in my favour. People with MCAS often report the same sensitivity, so it may mean that we experience effects at lower doses that more ‘normal’ immune systems may not. There are currently no controlled studies on microdosing GLP-1RAs, so everything at these doses remains anecdotal. Here’s my report:
- No weight loss: I was not looking to lose weight, and have instead been trying to up my protein and calories. Still, I was curious about effect on weight. At the small doses I’m using (now at 250 µg every 5 days), I do not have any reduction in weight. I do notice that my face is slimmer, which is likely due to the inflammation; with MCAS my face is often puffy and red.
- No worsening of spinal CSF leak symptoms: Given the research I recap below about intracranial hypertension and use of GLP-1RAs to lower intracranial pressure, I was very concerned that this class of medication could worsen my spinal CSF leak symptoms. The dosing for that research is considerably higher, and at this low dose I have not had any worsening of my “brain sag” or other symptoms associated with my spinal CSF leak.
- No anhedonia or fatigue: A documented side effect from these meds is anhedonia, the blunting of pleasure/joy, and some users report fatigue. While I do not crave sweets any longer for those few days pre-period that I used to, I do not find any less motivation, ambition, joy, or energy. If anything, my energy has increased, perhaps because of how much systemic inflammation I was carrying with my onion of conditions. Given what we know about inflammation’s negative effect on mood, it made me wonder. Either way, I am not complaining.
- No change or increase in constipation. To my knowledge, I do not have gastroparesis but you may have seen that it is a known potential side effect for GLP-1RAs. Gastroparesis is a chronic disorder that is commonly comorbid with Ehlers Danlos Syndrome, and involves delayed stomach emptying without a blockage. This lack of motility, the muscle movements within your GI tract that move food forward through the digestive process, causes nausea, vomiting, and premature fullness. I used to be quite regular on the pooping front, but since starting antihistamines for MCAS I have had to take magnesium oxide to stay regular; fibre in food has not been sufficient to keep things moving. I was concerned that starting tirzepatide would make things worse on that front. In my case and at this small dose of medication, I have not noticed any changes to my usual schedule.
- Some nausea: I did have some nausea after eating after my first dose, especially after eating something higher in fat. It ebbed and reappeared again around week four, which makes sense from what we know of tirzepatide’s half-life (of approximately five days), as it takes roughly four to five weeks of regular dosing to reach a “steady state” in the body where drug levels stabilise at a consistently higher baseline than in the early weeks. As I adjusted to the dosing, the nausea went away.
- Shorter dosing to smooth troughs: Common in discussion of GLP-1RAs online is the complaint that toward the end of the dosing window, people feel extra hungry or symptoms return. I found that my pain and mast cell sensitivity was worse on days six and seven of my seven day schedule. At this smaller dose, some patients were taking the medication on a five-day schedule instead of seven-days.
- Way less pain: At this dosing, I have been surprised to feel considerably less joint pain and nerve pain, despite an ongoing spinal CSF leak. This has not allowed me to do more with a leak, but has given me a much-needed reprieve in the onslaught of pain and meant I can tolerate a little more uptime. Being in chronic pain is itself so exhausting, eating up so much mental bandwidth, that the extra space it opened up has been a wonder. My hands and feet often swelled up and were burning and painful at night; this has also gone away.
- Less MCAS reactions and flares; more food tolerance: At this dosing, I have also seen a reduction in flares and reactions normally attributable to my mast cell dysfunction. I have been able to consume foods that caused significant reactions for the last 8 years: plain Greek yoghurt, regular consumption of gluten free oats, kiwifruit (yay!), coconut aminos for some umami when cooking, mild curry pastes (Keralan or Massaman curries), and more. The rashes on my arms and legs have faded noticeably. As spring approaches, I am curious to see how I fare with pollen season. Usually, this time of year is very painful for me. A brief example: one of my worst triggers is smoke. I have woken up with my throat closing and burning all over in the middle of the night because someone in my building is smoking (though it is a non-smoking building!), and needed rescue meds each time. Yesterday, I woke up to the faint smell of weed in my unit and a very painful throat, but I slept through it for the first time in four years. I’ve never not woken up due to reactions like this before.
- No hair loss: There are a lot of anecdotal reports of hair loss, especially a few months into these medications at standard doses, or some microdoses. I have not yet experienced this, but will update this section if I do. I’ve been on this microdose thus far for several months.
So why are these medications helping us, even at these mini doses?
One possible explanation is that the anti-inflammatory and neuroimmune effects of GLP-1 receptor activation may occur at lower levels of receptor engagement than the metabolic effects (like weight loss or appetite suppression). Essentially, the threshold for ‘quieting’ inflammatory action / modulating inflammatory signalling may be lower than the threshold for affecting body weight. This explanation is still a hypothesis from different papers, but it is consistent with how these medications act across different conditions.
GLP-1RAs as a support for MCAS
For some basics: glucagon-like peptide-1 receptor agonists (abbreviated as GLP-1 medications or as I noted above, GLP-1RAs) are a class of medications that includes semaglutide (Ozempic/Wegovy) and tirzepatide (Mounjaro/Zepbound, which also work on GIP receptors), as well as in-trials Retatrutide (a triple agonist that works on GLP-1, GIP, and Glucagon receptors).
These medications were originally developed to manage type 2 diabetes and, later, obesity, but a growing body of research suggests they also have broad anti-inflammatory and immunomodulatory effects across multiple organ systems.
The anti-inflammatory mechanisms of GLP-1RAs include that they can reduce inflammation through inhibition of nuclear factor kappa B (NF-κB) signalling, can reduce proinflammatory cytokine signalling (these cytokines are also released by mast cells), and can modulate immune cell activity. What I didn’t know until I started my rabbit hole was that GLP-1 receptors are found on immune cell types like T cells, B cells, macrophages, eosinophils, and on mast cells themselves.
So GLP-1 medications, it seems, help shift the immune system toward a more tolerant, less “I’m a feral child” state. What made me interested in trying them is when I read about how the anti-inflammatory properties of the medications aren’t only possible with weight loss or glycemia. Meaning, they can still have an impact on the body at lower doses, doses that wouldn’t provoke weight loss.
What is happening with inflammatory signalling that is separate, and helpful? Again: not a doctor. But what seems to come up repeatedly, even among conditions that don’t appear to be related, are the receptors themselves. GLP-1 receptors are expressed both centrally (in the brain) and peripherally (in immune cells, the gut, and metabolic tissues). This means the medications aren’t acting on just one pathway, but on many of them at once. They influence appetite regulation, inflammatory signalling, autonomic tone, and increasingly, are being studied in the context of CSF dynamics and CSF pressure disorders. For those of us with complex, multi-system conditions like MCAS or heritable connective tissue disorders, it may translate into improvements across multiple areas of dysfunction.
For patients with MCAS specifically, what piqued my interest in giving this class of medications a try was a case series in The American Journal of the Medical Sciences from mast cell experts, including doctors Afrin, Weinstock and Dempsey. Among 47 cases with patients with confirmed MCAS, many of whom had not responded adequately to prior therapies, the case series found that 89% demonstrated clinical benefit with GLP-1RAs across a broad range of symptoms. In several cases improvements were very quick, with symptoms dramatically improving or resolving shortly after starting low-dose GLP-1RA therapy. Improvements included inflammatory, neurological, gastrointestinal, and autonomic symptoms. These patients, like me, also had minimal side effects. The average age of those 47 patients was 39 years old, with a range of 15–71 years old. 89% of them were female.
The authors of the study emphasized a “start low, go slow” approach to initiating GLP-1RA therapy, something that they note can help reduce initial nausea and other gastrointestinal issues I wrote about above. Importantly to me, these medications are theorized to also exert mast cell–stabilizing effects at these doses. Instead of targeting individual mediators the way antihistamines do, they may help reduce mast cell activation more upstream, potentially dampening the downstream inflammatory cascade.
Also of note is that the doses used in the case series varied. The paper suggests initiating therapy at roughly 10–25% of standard starting dose for type 2 diabetes or obesity, which for tirzepatide (approved starting dose 2.5 mg) would be roughly 250–625 µg, or 0.25 – 0.625 mg. At those doses, many of the patients did also experience weight loss, but no patient became underweight.
The authors are careful to note the study’s limitations, and I want to mention them here. It is a retrospective case series, not a randomized controlled trial, for one. As such, it is subject to selection bias and cannot establish causality. The authors describe the high clinical benefit rate in their cohort as “a clarion call for rigorous, systematic investigation”, but thus far there has been no large-scale or prospective, controlled investigation for MCAS.
Use of GLP-1RAs for other conditions
One thing is for sure, despite this class of medications being primarily sold for diabetes and now for weight loss, they are being investigated for much more beyond their potential use for MCAS. At the time of writing, there are hundreds of trials actively recruiting for participation listed on ClinicalTrials.gov.
In cardiovascular disease, studies have found these medications provide cardiovascular protection, with a 14–20% reduction in major adverse cardiovascular events (MACE), a benefit understood to be at least partially mediated by anti-inflammatory pathways rather than glycemic control alone.
Reinforcing this, in heart failure with preserved ejection fraction, randomized trials such as the STEP-HFpEF program published in the New England Journal of Medicine demonstrated improvements in symptoms and physical limitations, with benefits that could not be fully explained by weight loss alone.
This class of medications has also been discussed in the context of lipids. In clinical studies, GLP-1 receptor agonists have been associated with modest reductions in LDL cholesterol and total cholesterol, with more variable effects on triglycerides depending on the specific agent and study population. A 2025 meta-analysis of 33 placebo-controlled randomized trials involving nearly 6,000 participants found that GLP-1RAs modestly (but significantly) reduced LDL cholesterol and total cholesterol, and interestingly, weight change did not influence these lipid outcomes. Whatever is going on seems like it may be a direct metabolic mechanism separate from loss of appetite (or weight). Like I said, though, modest reductions: LDL dropped by roughly 3 mg/dL on average, and there was no significant effect on triglycerides or HDL in that analysis. Tirzepatide specifically, as a dual GLP-1/GIP agonist, showed more pronounced reductions in LDL, triglycerides, and total cholesterol compared to placebo and SGLT2 inhibitors in a different paper. Note that for those of us using microdoses: there is no data on lipid effects at these lower doses, but since lipid benefits at standard doses are modest, there may be no change at lower amounts. I’m curious how my labs look after 6 months of use; given we do know mast cell dysfunction can negatively impact lipids, I guess we will see if there will be any positive effects! (Research has identified mast cells as one of the immune cell types involved in the inflammatory cascades that influence arterial plaque development and lipid-related cardiovascular risk, as I note in my MCAS info page.)
In neurological disease, research in animal models of stroke and vascular dementia has shown that GLP-1RAs reduce both microglial activation and neuroinflammation, leading to better protection of the brain from injury and cognitive deterioration. A 2024 double-blind randomized trial of 156 participants with early Parkinson’s disease found that participants receiving a GLP-1 drug, lixisenatide, showed no progression of motor symptoms, compared to a measurable worsening on standard motor scales in the placebo group. A different randomized trial of exenatide (a GLP-1RA sold as Byetta or Bydureon) in Parkinson’s patients also showed benefit, and the effects persisted even after a washout period following treatment. An accompanying editorial to the study noted that if the benefit is cumulative, adding roughly three motor-score points of protection per year over 5-10 years, then this class of drugs could prove transformative for a disease that currently has few disease-modifying interventions. Larger trials of semaglutide for Alzheimer’s disease are expected to report results in 2026.
In gastrointestinal inflammatory conditions, observational data suggest that GLP-1RA use in patients with inflammatory bowel disease is associated with a lower risk of IBD-related surgery in both ulcerative colitis and Crohn’s disease, and early studies have explored whether GLP-1RA injections can reduce pain in irritable bowel syndrome patients (the answer was yes). Irritable bowel syndrome is a condition that frequently co-occurs with MCAS.
There is also research into the benefit of GLP-1RAs for the liver. Specifically for MASH, metabolic dysfunction-associated steatotic liver disease (renamed from nonalcoholic fatty liver disease). Weight loss may play a role for liver health in patients, but with Ehlers-Danlos Syndrome (EDS) and MCAS, liver disease is not uncommon even when very slender. Semaglutide has been shown to improve liver labs, modulate lipid metabolism, and lower hepatic inflammation, with effects that appear at least partly independent of weight loss. Based on interim phase 3 data from the ESSENCE trial, the Wegovy-branded formulation of semaglutide received accelerated approval in the United States in 2025 for adults with MASH and moderate-to-advanced fibrosis. In that trial, 62.9% of participants achieved resolution of steatohepatitis without worsening fibrosis at 72 weeks, compared to 34.1% with placebo. Tirzepatide has shown similar results: in a phase 2 trial, up to 73.3% of participants at the highest dose achieved MASH resolution without worsening fibrosis at 52 weeks, compared to 13.2% on placebo. Meta-analyses and large observational papers further suggest that GLP-1RAs are associated with a reduced risk of liver-related clinical events, like progression to cirrhosis. As with the lipid findings, I want to be clear that these results come from standard or near-standard doses, so my microdoses are not likely to produce anything close to this level of change. But for readers with fatty liver disease alongside MCAS or other inflammatory conditions, this is now one of the more evidence-supported areas for this class of medications and may be worth a conversation with your physician!
Back to something related to my chaotic mess of medical conditions: intracranial pressure. In the context of IIH (idiopathic intracranial hypertension), and RIH (rebound intracranial hypertension), the body’s inability to regulate the increase in CSF volume once a patient is sealed, GLP-1 medications are also starting to get attention. A randomized trial using the GLP-1 agonist exenatide in people with IIH showed that intracranial pressure dropped within hours to days of dosing, far too quickly to be explained by any weight changes. This suggests a more direct effect on CSF dynamics, potentially via GLP-1 receptors in the choroid plexus that may influence CSF production. For those of us thinking about pressure regulation more broadly, it’s intriguing. Many long-term spinal CSF leak patients vacillate between high and low pressure, and anecdotally some are finding support with these medications at microdoses to help regulate their CSF dynamics.
What else? Research is underway for additional neurological disorders, dermatological conditions, respiratory diseases, addictions (food and otherwise), and more.
GLP-1RAs aren’t a cure, and there are downsides.
One thing worth addressing directly, because I’ve seen it come up in my inbox and online discussions: these medications are not a cure. Not a cure for MCAS, nor for anything else they’ve been shown to help. The literature is fairly consistent on this point across the conditions I’ve listed out above.
In weight loss trials, a substantial proportion of patients regained a significant amount of weight within a year of stopping GLP-1RAs. In the MASH liver trials, discontinuation studies are still limited, but early data suggests liver enzyme improvements and histological gains are not maintained without ongoing treatment. And in the MCAS case series, most patients who stopped their GLP-1RA (whether due to cost, unavailability, or curiosity about what would happen) experienced a return of the symptoms that had been controlled.
This class of medications can support my immune system much like a mast cell stabilizer does. Ketotifen or cromolyn don’t cure MCAS either, they help keep the water in my “Mast Cell Bucket” low. If I were to stop them, the water would overflow again. Same here: there is meaningful, sometimes dramatic change, but it is contingent on continued use.
It is also worth noting that GLP-1RAs are not without complexity in the chronic illness world, especially for patients with EDS or significant gastrointestinal dysmotility. I was very worried about delayed gastric emptying as I have EDS, and worried about additional constipation. This hasn’t been a problem for me, but for those of you with gastroparesis it is especially important to work with your medical professional and have them confirm that it is safe for you to start at even low doses, as it may not be. Known side effects at standard doses include delayed gastric emptying, gallbladder-related issues, and more rarely, a risk for acute pancreatitis, though as mentioned above these appear to be less common at lower doses.
I’m hoping for randomized controlled trials for microdoses, to establish optimal dosing. In the absence of them, I am yet again my own n=1, as I have been for the last many years. The inital MCAS paper was sufficiently compelling for me to give them a try, and in my case they have helped me tolerate more food, more uptime, and have more energy. With a chronic spinal CSF leak and other comorbidities, this is a welcome sliver of relief.
References
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