If you're taking a GLP-1 medication, or thinking about starting one, you may be wondering what it means for your gut health. It's a question we hear frequently from MAT users.
Many medications are known to affect the gut microbiome. Antibiotics can dramatically disrupt gut bacteria, while other commonly prescribed drugs, including metformin and some antidepressants, have also been shown to alter the microbial community, sometimes in ways that may not be beneficial.
So it's natural to ask: Do GLP-1 medications also change the gut microbiome?
The short answer is: we don't know yet, but the evidence so far is reassuring.
What Are GLP-1 Medications?
GLP-1 medications include Ozempic and Wegovy (semaglutide), as well as Mounjaro and Zepbound (tirzepatide). They were originally developed to improve blood sugar control in people with type 2 diabetes. Researchers later discovered that these medications also slow stomach emptying, increase feelings of fullness, and reduce appetite, helping many people eat less, lose weight, and improve their metabolic health. Their use has expanded rapidly in recent years. Today, millions of people worldwide are taking GLP-1 medications, making it increasingly important to understand their long-term effects, including how they may influence the gut microbiome.
Future posts will address practical questions such as how to eat well while taking GLP-1 medications, how to support a healthy gut during treatment, and what to expect when stopping therapy. Here, we focus on a slightly different question than most published microbiome studies.
Most research asks whether GLP-1 medications change which microbes are present in the gut in other words, the microbiome's composition. That is an important question, but it captures only part of the picture. The MAT is designed to monitor a different aspect of gut health. Rather than identifying which bacteria are present, it uses fecal pH as a scientifically supported proxy for microbial metabolic activity, a measure of how actively the gut microbiome is functioning. This distinction matters because health depends not only on who is there, but also on what they are doing. We are actively studying whether GLP-1 treatment influences this functional dimension of gut health over time.
What Does the Research Say?
Two recent scientific publications help answer this question.
Study 1: Evidence Suggests Changes, But the Picture Is Complicated
A 2025 review by Gofron and colleagues analyzed the available research on GLP-1 medications and the gut microbiome. The authors concluded that while GLP-1 drugs may influence the composition, richness, and diversity of gut microbes, the current data has a major limitation. At the time of publication, there were very few human trials and virtually no direct studies on how semaglutide affects the human microbiome. Consequently, the findings remain inconsistent. Some studies showed increases in Akkermansia muciniphila, a bacterium associated with good metabolic health, while others reported a drop in microbial diversity or no clear changes at all.Why the conflicting results?
The review identified several reasons:
- Studies ranged from 8 weeks to a full year.
- Different studies used different microbiome analysis methods.
- Many participants were also taking medications such as metformin, which independently affects the microbiome.
- Diet and lifestyle changes during weight loss were often not fully accounted for.
In other words, it remains difficult to determine whether any microbiome changes are caused by the medication itself or by the healthier lifestyle and weight loss that often accompany treatment. Additionally, most of these studies measured microbiome composition using DNA sequencing. While this reveals which bacteria are present and in what amounts, it does not show how active those microbes actually are.
Study 2: A Year-Long Human Study Finds Little Direct Effect
A recent study by Klemets and colleagues (2026) provides some of the strongest evidence on this topic to date. Researchers followed individuals with type 2 diabetes for 12 months, collecting stool samples at four distinct intervals. This long-term tracking is significant, as most previous research only analyzed the microbiome once or twice over much shorter periods.
While the researchers primarily wanted to see if a participant's baseline microbiome could predict how well they would respond to treatment, they also tracked whether semaglutide itself altered the microbiome. Their primary finding was unexpected: semaglutide did not directly cause significant changes in the overall composition or diversity of the gut microbiome. Instead, they concluded that any microbial changes observed over the year-long period were likely driven by improvements in metabolic health, weight loss, diet, and lifestyle adjustments, rather than the drug itself.
However, the study does have one notable limitation: the participants had previously taken metformin, a medication already known to alter the gut microbiome, which may have obscured some of semaglutide's direct effects. Additionally, like previous research, this study only measured microbiome composition rather than microbial function. Even if the overall bacterial population remains stable, the biochemical activity of those gut microbes may still shift as patients lose weight, manage their blood sugar, and adopt healthier eating habits.
What Does This Mean for MAT Users?
The current scientific evidence suggests that GLP-1 medications do not dramatically reshape the gut microbiome the way antibiotics do, which can cause substantial disruption to microbial communities. That said, this does not mean nothing is changing.
GLP-1 treatment frequently produces significant shifts in food intake, dietary quality, body weight, blood sugar regulation, and intestinal physiology. Each of these factors can influence how gut microbes function, even when the overall composition of the bacterial population remains relatively stable. This distinction between microbial composition and microbial function is increasingly recognized within microbiome science. Modern DNA sequencing can tell us which microbes are present, while functional measurements reveal what those microbes are actually doing.
The MAT complements both of these approaches by tracking fecal pH, a practical marker of microbial metabolic activity. Taking repeated measurements over time can help reveal how your gut microbiome responds as your diet, lifestyle, and metabolic health continue to evolve throughout GLP-1 treatment.
Let's Review and Summarize
Current research suggests that GLP-1 medications have little direct effect on the overall composition of the gut microbiome. Most of the changes observed during treatment appear to reflect improvements in diet, weight, metabolism, and other lifestyle factors rather than the effect of the medication itself. One important question remains unanswered: whether these improvements are accompanied by meaningful changes in microbial function, the biochemical activity of the gut ecosystem. This is an area where research is only beginning to take shape.
As the use of GLP-1 medications continues to grow, understanding both the composition and the function of the gut microbiome will become increasingly important. We are excited to follow this emerging science and to continue investigating how microbial metabolic activity shifts over the course of GLP-1 treatment.
References
Klemets A, et al. Fecal microbiome predicts treatment response after the initiation of semaglutide or empagliflozin uptake. Scientific Reports. 2026.
Gofron KK, et al. Effects of GLP-1 Analogues and Agonists on the Gut Microbiota: A Systematic Review. Nutrients. 2025.
