Bloating is extremely common in people with fibromyalgia. Over half of fibromyalgia patients meet criteria for a functional gastrointestinal disorder, and about 46% have co-occurring irritable bowel syndrome, where bloating is a hallmark symptom. That rate is roughly four times the global prevalence of IBS in the general population. So while fibromyalgia isn’t typically thought of as a digestive condition, gut symptoms like bloating, distension, and abdominal discomfort are part of the picture for many people living with it.
Why Fibromyalgia Affects Your Gut
The connection comes down to how your nervous system processes signals. Fibromyalgia involves a state called central sensitization, where the brain and spinal cord become hyper-responsive to incoming sensory input. Normal signals that shouldn’t register as painful get amplified. This doesn’t only apply to muscles and joints. The same heightened processing affects signals coming from your digestive tract, a phenomenon known as visceral hypersensitivity. Gas or movement in your intestines that a healthy nervous system would ignore can register as painful pressure or fullness.
There’s also a direct communication highway between your gut and your brain, and in fibromyalgia it appears to malfunction in both directions. Disruption of this gut-brain connection, whether from changes in gut bacteria, a weakened intestinal lining, or altered chemical messengers produced by microbes, has been linked to chronic pain, fatigue, mood changes, and that amplified sensitivity to normal digestive sensations. In practical terms, this means your gut may be functioning relatively normally, but your brain is interpreting its activity as bloating, pain, or discomfort.
The Fibromyalgia-IBS Overlap
The relationship between fibromyalgia and IBS is strong and runs both ways. A systematic review pooling data from 14 studies found that 46.2% of people with fibromyalgia also have IBS. Looking at it from the other direction, between 28% and 65% of people diagnosed with IBS also meet criteria for fibromyalgia. The odds of having fibromyalgia are 1.8 times higher if you already have IBS.
This isn’t a coincidence. Both conditions are thought to share the same underlying mechanism: a nervous system stuck in overdrive. If you have fibromyalgia and experience regular bloating along with changes in bowel habits (constipation, diarrhea, or alternating between the two), there’s a reasonable chance you also meet the diagnostic criteria for IBS. Getting that recognized matters because it opens up additional treatment options specifically targeting your gut symptoms.
Changes in Gut Bacteria
People with fibromyalgia show measurable differences in the makeup of their gut microbiome. Several beneficial bacterial species are depleted, including types that produce short-chain fatty acids, which are compounds that nourish the intestinal lining and help regulate inflammation. When these bacteria are reduced, the gut lining can become more permeable, potentially allowing bacterial byproducts to trigger low-grade immune responses.
There are also significant changes in bacteria that help process bile acids. Some of these bile acids have natural pain-relieving properties, and their depletion in fibromyalgia patients may contribute to both heightened pain sensitivity and digestive dysfunction. One small study found that 100% of fibromyalgia participants tested positive for small intestinal bacterial overgrowth (SIBO), a condition where bacteria proliferate in the wrong part of the digestive tract and produce excess gas, though that finding hasn’t been replicated. Still, it points to the gut as a meaningful piece of the fibromyalgia puzzle, not just a bystander.
Medications That Make It Worse
Some of the drugs commonly prescribed for fibromyalgia can contribute to bloating on their own. Pregabalin (Lyrica), one of the three medications specifically approved for fibromyalgia, lists constipation, weight gain, increased appetite, and swelling of the hands and feet among its side effects. Constipation alone can cause or worsen bloating significantly. Other common fibromyalgia medications can cause nausea, constipation, and decreased appetite, all of which alter how your digestive system moves things along.
If your bloating worsened after starting a new medication, that timing is worth noting. It doesn’t necessarily mean you should stop the drug, especially if it’s helping your pain, but it’s useful information for adjusting your overall treatment plan.
What Helps (and What Doesn’t)
The low-FODMAP diet is one of the most well-studied dietary approaches for IBS-related bloating. It works by temporarily eliminating fermentable carbohydrates (found in foods like onions, garlic, wheat, and certain fruits) that feed gas-producing bacteria. For people with IBS alone, this diet reliably reduces bloating and distension. For people who have both IBS and fibromyalgia, the picture is less clear.
A study tracking patients on a low-FODMAP diet over time found that those with IBS alone saw significant improvement in abdominal distension severity, but those with co-occurring fibromyalgia did not reach statistical significance. Both groups reported some reduction in how often they experienced bloating, but the improvements were modest and inconsistent in the fibromyalgia group. This suggests that when central sensitization is part of the equation, dietary changes alone may not be enough to resolve the symptom. The bloating isn’t purely a gut problem; it’s also a nervous system problem.
That doesn’t mean dietary changes are useless. Reducing known trigger foods, eating smaller meals, and staying hydrated can take some pressure off a sensitized system. But the most effective approach likely combines gut-focused strategies with treatments that address central sensitization itself, whether that’s regular low-impact exercise, stress reduction techniques, or medications that calm overactive nerve signaling. Addressing just the gut or just the pain, without recognizing how they feed each other, tends to leave people frustrated with incomplete relief.