Long-Term NSAID Use Side Effects Your Stomach Will Not Warn You About

He is sixty-eight and carries his prescriptions in a plastic bag: nine bottles, including a daily anti-inflammatory for his knees and a low-dose aspirin for his heart. He also carries bloating, bowels that swing between loose and stalled, and a tiredness written off as age. Nobody had connected the knee pill to the belly, because nobody looks at the small intestine of a man whose stomach feels fine.

That blind spot is where most long-term NSAID use side effects live. The video Two-Thirds of Your Pill Is Not the Drug walks through his whole bag. Here I want to stay with the one bottle nearly every pain patient has owned, and with the injury it causes where nobody is looking.

A good drug with a blind spot

An anti-inflammatory quiets an angry joint fast. That is why it ends up in so many bags, and why the conversation about it tends to stop at the joint. The Angry Gut, by Dr. Gurpreet Singh Padda, MD, MBA, MHP, and Ami Michelle Grimes, calls the gut the first brain: a living surface of about thirty-two square meters that meets every tablet at full strength on the way through. The second brain, in the skull, hears about the damage late or never.

What a capsule camera found after two weeks

Investigators gave 40 healthy volunteers an ordinary anti-inflammatory dose for two weeks, then had them swallow a capsule camera. New pathology showed up in 27 of them. A stool marker of gut inflammation rose above normal in 30, and 16 had frank breaks in the lining.

The details rarely get quoted. Reddened folds appeared in 14 people, pinpoint red spots in 13, stripped lining in 8, and blood with no visible source in 3. Fifteen of the 27 affected volunteers had more than one kind of lesion at once. None of them came in with a complaint.

A normal-feeling belly is not a normal-looking bowel.

Long-term NSAID use side effects build with time

Two weeks is the short version. In chronic users, visible small-bowel injury appeared in 71%, against 10% of controls. The severity split matters more. Ten users had mild injury and five had major damage, meaning more than four erosions or large ulcers, while controls had two mild cases and no major ones. It was a small study, and the users had arthritis while the controls did not.

Duration pushes the numbers up. Among rheumatoid arthritis patients on an anti-inflammatory for more than 12 months, 13 of 16 had mucosal breaks, compared with 4 of 12 not taking one. Among heart patients on enteric-coated low-dose aspirin, 10 of 11 had breaks, and one person had 33 of them.

Across the literature, the summary figure is around half of chronic users with visible injury, most of them without symptoms. Enteric coating is the protection people believe they have. It protects the stomach.

Two other drivers sat right beside the drug. In a health-check population of 1,599 people, aspirin users had small-bowel breaks at 36.9% against 6.3%. In that same population, obesity carried an odds ratio of 2.30 and smoking 1.85, independent of the pill. Location differed too: aspirin injury clustered in the jejunum, background injury in the ileum. A medication review that ignores weight and tobacco does only part of the job.

The acid blocker guards a different organ

Plenty of people take an anti-inflammatory with an acid blocker to spare the stomach. For the stomach, the logic holds up. In 133 patients who arrived bleeding from the upper gut, aspirin users aged 70 and over had about ninefold odds of overt bleeding, and regular acid suppression cut that risk by 90%. It was a small observational study of people who had already bled, so it speaks to severity, not to who bleeds.

Below the stomach, the answer flips. In a trial pairing celecoxib with rabeprazole or with placebo, small-bowel injury was 2.7 times higher in the group taking the acid blocker. One drug protects one organ and exposes the next. The only agent with a shown healing benefit for small-bowel ulcers in aspirin users, misoprostol, produced complete healing in 28.6% against 9.5% on placebo. That is modest.

None of that is a reason to change a prescription on your own. It is a reason to ask which organ a protective drug was chosen for, and whether anyone has asked about the other one.

When the permeability test comes back normal

A 2026 randomized trial gave healthy volunteers indomethacin and found no rise in intestinal permeability. That result gets used to call the whole concern overblown. Read the rest of it.

The volunteers felt the drug even though the assay missed it. Symptom scores rose from 15.5 to 17.3, and abdominal pain from 3.0 to 3.7, with intervals that did not cross zero. The placebo arms held 13 and 11 people, dosing ran six days, and the authors suggested that longer exposure, or a barrier already damaged, might have shown the effect. The barrier test was negative. The patients were not.

The older study that built that test holds a result every pain patient should know. In 23 healthy volunteers, indomethacin pushed the lactulose-to-mannitol ratio to 0.071, against 0.030 in the control condition. Public speaking raised it too, to 0.059. An injected stress hormone reproduced the effect, and a mast cell stabilizer blocked it.

Chronic pain is a stress state. A person who hurts every day runs a nervous system on alert, and the wall of the first brain answers stress hormones through mast cells. Add a daily anti-inflammatory and the same lining is being pressed from two directions at once.

Pain medicines leave fingerprints on the flora

The bag does not only touch the lining. In a laboratory screen of marketed drugs, 27% of non-antibiotics, 203 human-targeted drugs in all, inhibited at least one gut bacterial species, and the authors called that the conservative end of the estimate.

In people, specific classes leave specific marks. Antibiotic-resistance gene counts rose in opiate and tricyclic antidepressant users in a disease cohort, and in metformin and acid-suppression users in the general population. That is a marker of potential, not a resistant infection. And a drop in one gut microbe once read as a signature of depression turned out, across 1,802 people, to be explained by SSRI and SNRI use. The census counted the prescription and called it the disease.

Distinct fingerprints can be matched to distinct bottles. The same logic applies to opioids: a taper managed alongside interventional care is a medical decision, and stopping too fast carries harms of its own.

Bring the bag, not a typed list

For that patient, four things changed, all worked through with his cardiologist. The anti-inflammatory came off, and his knees finally got an exam. The acid blocker was tapered and reassessed. The laxative and multivitamin moved to versions without the fermentable sugars his dietitian had flagged. Everything with a live reason to be there stayed.

Knees are a pain practice's job. A joint silenced by a daily pill for years usually has a metabolic story too, which is why we treat insulin before we treat the joint. Once the joint is addressed directly, the anti-inflammatory can become an occasional tool rather than a daily exposure.

• Bring the actual bottles. The same drug from a different manufacturer is a different formulation.
• Write the start year beside each daily medicine. An eleven-year prescription is a different question from a two-week course.
• Ask three things of each bottle: what is it for, is that still true, and what am I accepting in exchange if it stops.
• Keep two weeks of dated symptom notes before any change and four weeks after.
• Stop nothing alone. Work every change through with the physician who prescribed it.

Every capsule study, and the trial that cuts against the argument, is laid out in the Chapter 2 Deep Dive, with what each study shows and does not show. For the groundwork on the first brain, start with The Angry Gut, Chapter 1. Next, how the vagus nerve carries the gut's complaints to the brain.

Frequently asked questions

Does ibuprofen cause bloating?

It can contribute, though bloating is an unreliable warning sign. Small-bowel injury from anti-inflammatories is usually silent, and most people with visible lesions on a capsule camera report nothing. Tablets also carry fermentable fillers: lactose sits in 45% of oral solid medicines. If bloating began with a daily pill, raise both the drug and its formulation with your physician. One medication list can cause problems no single prescriber sees.

Can NSAIDs cause diarrhea?

They can inflame the small intestine quickly. In healthy volunteers given an ordinary anti-inflammatory dose for two weeks, a stool inflammation marker rose above normal in three out of four. Loose stools alongside a daily anti-inflammatory deserve a look, not another medicine layered on top, and any change belongs with your physician. Some pain medicines quietly make pain and its companions worse.

Does an acid reducer protect my intestines from NSAIDs?

It protects the stomach, not the small intestine. In older aspirin users, regular acid suppression went with far less upper-gut bleeding. Further down, one trial found small-bowel injury 2.7 times higher when an acid blocker was added to celecoxib than when placebo was. Ask your physician which organ your protective drug was chosen for. Gut inflammation feeds the wider metabolic inflammation behind chronic pain.

Is enteric-coated aspirin easier on the gut?

Easier on the stomach, not on the small intestine. Among heart patients taking enteric-coated low-dose aspirin, 10 of 11 had small-bowel mucosal breaks on capsule endoscopy. The coating is protection for the stomach only. Never stop aspirin prescribed for your heart without talking to your cardiologist first. Anti-inflammatories carry a separate heart risk in type 2 diabetes.

How long does it take NSAIDs to damage the small intestine?

Damage can appear within two weeks: healthy volunteers developed new small-bowel findings in 68% after a two-week course. Time makes it more common. Among rheumatoid arthritis patients using an anti-inflammatory for more than 12 months, 13 of 16 had mucosal breaks. Duration is a good reason to revisit a daily prescription with your physician. Belly fat adds its own inflammatory load to the same picture.

Sources

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3. Sun, X., Wang, F., Liu, J., Wu, L., Wang, Z., Chen, X., Wang, M., & Zeng, Q. (2022). Risk factors for small-intestinal mucosal breaks beyond aspirin. Journal of Gastroenterology and Hepatology, 37(8), 1596–1602. https://doi.org/10.1111/jgh.15892
4. Watanabe, T., Fujiwara, Y., & Chan, F. K. L. (2019). Current knowledge on non-steroidal anti-inflammatory drug-induced small-bowel damage: a comprehensive review. Journal of Gastroenterology, 55(5), 481–495. https://doi.org/10.1007/s00535-019-01657-8
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Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP, board certified in anesthesiology, pain medicine, interventional pain management, addiction medicine and obesity medicine. Adapted from Chapter 2 of The Angry Gut by Dr. Padda and Ami Michelle Grimes. Last reviewed September 2026.

Dr. Gurpreet Singh Padda, MD, MBA, MHP