Diarrhea on a GLP-1? Could Bile Acid Malabsorption Be Involved?
Digestive side effects are a top cause of early discontinuation of GLP-1 medication. However, medication may not be the only cause of GI distress, and the true cause may require a little detective work. Bile-acid malabsorption (BAM) also causes chronic diarrhea and may be an alternative culprit. Let’s investigate.
What is BAM?
Bile acids are a byproduct of the liver that help our body break down dietary fats in the small intestine. The body then reabsorbs and recycles extra bile acids for future use. However, with BAM, the intestine does not properly reabsorb bile acids, so they exit the GI tract through the bowels. Common symptoms include watery or loose diarrhea, bowel urgency, smelly gas, or greasy stools. Common causes include Crohn’s disease, pancreatitis, side effects of surgical intervention to the GI system, or radiation therapy.
Could BAM Be Mistaken for GLP-1 Side Effects?
It is entirely possible. GLP-1 medications alter how our body digests food, leading to diarrhea as a commonly reported side effect. In fact, roughly 1/3 of GLP-1 users report diarrhea. Diarrhea is typically worse at initiation of the drug and may worsen as the dosage is titrated up. For many patients, diarrhea and other digestive side effects from GLP-1s resolve or improve over time as the body adjusts to the medication. If you start experiencing diarrhea after you begin taking a GLP-1, the likely presumption is that the medication is the cause, even if an underlying condition like BAM is the true offender.
When to Talk to Your Healthcare Provider About Persistent Symptoms
If you have been experiencing diarrhea or any of the above symptoms prior to starting a GLP-1, discuss this with your doctor. They may recommend addressing the cause before starting the medication if GLP-1 side effects worsen your GI function. On the other hand, if you start a GLP-1 and then begin experiencing diarrhea, see when it subsides. If diarrhea continues to worsen after several weeks or even months of taking the medication, it’s possible that BAM could be involved. Similarly, if you cease taking a GLP-1 but your symptoms don’t resolve on their own, it's time to probe further.
An Interesting Link Between GLP-1 and BAM
What’s very interesting about this relationship is that GLP-1s may be a potential remedy for BAM. Because GLP-1 slows down digestion, it is hypothesized that this gives the body more time to reabsorb and recycle bile acids. A 2025 trial using GLP-1 liraglutide showed improved symptoms compared with bile acid sequestrants. This research is still preliminary, and much more is needed to understand whether other types of GLP-1 will have the same effect and whether it can be a long-term solution.
Final Verdict
When it comes to our health, sometimes we jump to conclusions and blame the wrong suspect for our problems. It’s always good to play detective of our health, pay attention to patterns, and see how symptoms change over time. Keep the case open until you’ve had a chance to work with your healthcare provider and rule out whether BAM is at the source of your problems.
FAQs
What is BAM?
Bile acid malabsorption is a digestive condition that can cause diarrhea, fecal incontinence, and watery or greasy stool.
What are common GI side effects of GLP-1 agonists?
Common GI side effects include diarrhea, loss of appetite, delayed gastric emptying, and bloating.
Could BAM be mistaken for GLP-1 side effects?
Yes! If symptoms began prior to starting a GLP-1 or don’t improve following discontinuation of the medication, consider discussing BAM as a potential cause with your healthcare provider.
References
1Bozick, R., Donofry, S. D., & Rancaño, K. M. (2025). New Weight Loss Drugs: GLP-1 Agonist Use and Side Effects in the United States. Rand health quarterly, 13(1), 3. https://pmc.ncbi.nlm.nih.gov/articles/PMC12711338/
2Ellegaard, A. M., Kårhus, M. L., Winther-Jensen, M., Lund, A. B., & Knop, F. K. (2025). Treatment of Bile Acid Diarrhea With Glucagon-Like Peptide 1 Receptor Agonists: A Promising Yet Understudied Approach. Clinical and translational gastroenterology, 16(3), e00815. https://doi.org/10.14309/ctg.0000000000000815
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