IBS and the Low-FODMAP Diet: The Sugar Alcohols Hiding in Your Medication

If you are following a low-FODMAP diet for IBS, you have learned to read food labels closely. Medicine is easy to miss: some medicines are sweetened with polyols such as sorbitol and mannitol, the “P” in FODMAP. Monash University, which developed the diet, notes that these turn up in certain medications, particularly liquids. The lactose used in many tablets is a smaller concern: Monash says the amount is tiny and will not contribute to symptoms. Either way, the answer is never to stop a medicine on your own, but to ask your pharmacist about an alternative.

Which FODMAPs turn up in medicines and supplements

• Polyols (sugar alcohols). Sorbitol, mannitol, xylitol, maltitol, and isomalt sweeten foods and some medicines. Monash explains that sorbitol and mannitol are absorbed slowly and often incompletely, so they draw water into the bowel and are fermented by gut bacteria, which can mean bloating, pain, and changed bowel habits. The FDA lists cough syrup, chewable vitamins, over-the-counter medicines, and dietary supplements among the products that may contain xylitol. Our sugar alcohols guide covers them in depth.
• Lactose. A common tablet filler. Monash’s label-reading guidance says only people with lactose intolerance need to limit lactose, and that the tiny amounts in medications will not contribute to symptoms. Our lactose guide covers when that can change, such as high sensitivity or several lactose-containing medicines a day, and the separate case of milk allergy, where the concern is milk protein rather than FODMAPs.
• Prebiotic fibers. Monash notes that products making gut-health claims often add inulin, chicory root, fructooligosaccharides (FOS), or galactooligosaccharides (GOS), which can cause gas and bloating in some people with IBS. If you take a fiber or gut-health supplement, read its label the same way; our guide to ingredients in vitamins and supplements explains how supplement labels are laid out.

Liquids and chewables, not the tablet’s lactose

Monash’s guidance does not give amounts per dose for medicines, so be careful with any number you see quoted. What it does say points in a clear direction. Polyols are the FODMAP to look for, and a 2018 Monash article says they are found particularly in liquid medicines. Even then, the same article notes they may be present in very small quantities that are unlikely to cause gut side effects. The lactose in medications is the other candidate, and Monash treats it as too small to matter.

Your own tolerance matters too. Monash says you may not need to avoid all polyols to manage IBS, and during the reintroduction step of the diet, sorbitol and mannitol can be tested separately. Those results are your best guide to whether a polyol in a medicine is likely to matter to you.

What to do

• Read the inactive ingredients. On over-the-counter products they are in the Drug Facts panel; for a prescription, ask your pharmacist. Our guide to reading a drug label shows where to find them.
• Look hardest at liquids, syrups, and chewables, and ask whether a tablet, capsule, or polyol-free version of the same medicine exists.
• Tell your dietitian what medicines you take. Monash recommends following the diet with a dietitian who specializes in IBS, and your medicines are part of the picture during Step 1, the strict phase, which Monash sets at 2 to 6 weeks.
• Ask your pharmacist or doctor if you think a medicine is making your symptoms worse, rather than stopping it.
• Check the exact product with the app. The AllergenMeds app flags ingredients like these in the exact product you look up.

This guide is for education only, not medical advice. Always talk to your doctor or pharmacist before starting, stopping, or switching any medication.