Gastroparesis is diagnosed by confirming two things: your stomach empties food slower than normal, and there’s no physical blockage causing the delay. The standard test is a gastric emptying study, where you eat a small meal and doctors track how quickly it leaves your stomach over four hours. But getting to that test involves several steps, starting with ruling out other conditions that can mimic the same symptoms.
Symptoms That Prompt Testing
The hallmark symptoms of gastroparesis are nausea, vomiting, feeling full after just a few bites (early satiety), a lingering sense of fullness after meals, and upper abdominal pain. Doctors sometimes use a standardized scoring tool called the Gastroparesis Cardinal Symptom Index to track how severe these symptoms are. Each symptom is rated from 0 (none) to 4 (very severe), and vomiting is scored by the number of daily episodes. The combined score helps gauge overall severity and can be used later to measure whether treatment is working.
These symptoms overlap with a long list of other conditions, including peptic ulcers, celiac disease, and functional dyspepsia. That’s why diagnosis is never based on symptoms alone.
Ruling Out a Blockage First
Before any motility testing, your doctor needs to confirm that nothing is physically blocking food from leaving your stomach. This is typically done with an upper endoscopy, where a thin, flexible camera is passed through your mouth and into your stomach and upper small intestine. The procedure checks for ulcers, tumors, scar tissue, or narrowing at the stomach’s outlet.
One important detail: if the endoscopy reveals undigested food sitting in your stomach (something called retained gastric food), that alone does not confirm gastroparesis. Certain medications, particularly opioids and some diabetes drugs, can slow emptying temporarily. Food in the stomach during an endoscopy is a clue, not a diagnosis.
Blood Tests to Identify Underlying Causes
Gastroparesis is often a consequence of another condition rather than a standalone problem. Diabetes is the most common identifiable cause, because chronically high blood sugar damages the nerves that control stomach contractions. Thyroid disorders, autoimmune conditions, and other metabolic problems can also slow gastric emptying. Your doctor will likely order blood work to check blood sugar control, thyroid function, and markers of inflammation or autoimmune activity. In many cases, though, no underlying cause is found, and the diagnosis is labeled idiopathic gastroparesis.
The Gastric Emptying Study
The gastric emptying scintigraphy, often just called a gastric emptying study or GES, is the gold standard test. It’s straightforward but time-consuming. You eat a standardized meal, typically an egg white omelet on toast, that has been tagged with a tiny amount of a radioactive tracer. Then you lie under or stand in front of a scanner that takes images of your stomach at set intervals to measure how much food remains.
The test runs for four hours, with images typically captured at the one, two, and four-hour marks. Normal emptying follows a predictable pattern:
- At 1 hour: 90% or less of the meal should remain in the stomach
- At 2 hours: 60% or less should remain
- At 4 hours: 10% or less should remain
If more than 10% of the meal is still in your stomach at four hours, or more than 60% remains at two hours, the result is classified as delayed gastric emptying. The test can be stopped at three hours if more than 90% of the meal has already emptied, since there’s no need to wait longer when results are clearly normal. But cutting the test short at one or two hours, which some facilities do to save time, significantly reduces accuracy and can produce misleading results.
Preparing for the Test
Several medications can artificially speed up or slow down stomach emptying, which would skew the results. You’ll typically need to stop taking opioid pain medications, certain nausea drugs, and medications that affect gut motility for a period before the test. GLP-1 receptor agonists, a class of drugs commonly used for diabetes and weight loss, are particularly important to discontinue because they directly slow gastric emptying. Your ordering doctor should give you specific instructions on which medications to pause and for how long.
You’ll also need to fast overnight before the test. If you have diabetes, your blood sugar should be reasonably controlled on the day of testing, because high glucose levels at the time of the scan can independently slow emptying and create a false positive result.
Alternative Tests
Not every facility has scintigraphy equipment, and some patients can’t tolerate the standard egg meal. Two alternatives are recognized by the American College of Gastroenterology, though both carry conditional recommendations and weaker supporting evidence.
Wireless Motility Capsule
This is a small, swallowable capsule equipped with sensors that measure pressure, temperature, and acidity as it travels through your entire digestive tract. When the capsule drops out of the acidic stomach environment and into the more alkaline small intestine, the pH shift marks the moment of gastric emptying. A gastric emptying time longer than five hours is considered delayed. The capsule has a specificity of 87%, meaning it’s good at correctly identifying people who don’t have gastroparesis, but its sensitivity is only 65%, meaning it misses about a third of true cases. It does offer the bonus of evaluating motility throughout the entire gut, which can be useful if small bowel or colon transit problems are also suspected.
Breath Test
The stable isotope breath test uses a meal containing a special form of carbon (carbon-13) bound to spirulina, a type of algae. As the meal empties from your stomach and gets absorbed in the small intestine, the carbon-13 appears in your breath. The rate at which it shows up reflects how quickly your stomach emptied. Compared to scintigraphy, the breath test has a sensitivity of about 89% and specificity of 80% for detecting delayed emptying, using breath samples collected at just two time points (150 and 180 minutes). It’s radiation-free, making it a practical option for children and for patients who need repeated testing.
Tests That Are Not Recommended
Radiopaque marker testing, where you swallow small plastic markers and get X-rays to see where they are, is not considered reliable for diagnosing gastroparesis. The ACG guidelines specifically recommend against it. The markers are solid objects that don’t behave the same way food does in the stomach, so results don’t accurately reflect meal emptying.
Specialized Testing for Complex Cases
In patients with confirmed delayed emptying who aren’t responding to standard treatments, or when the diagnosis remains uncertain, doctors sometimes turn to antroduodenal manometry. This involves placing a thin pressure-sensing catheter through the nose and into the stomach and upper small intestine to directly measure the strength and coordination of muscle contractions. The test can distinguish between two broad categories of dysfunction: problems with the muscles themselves, and problems with the nerves directing those muscles. In nerve-related cases, the normal rhythmic contraction pattern that sweeps food through the stomach during fasting becomes disorganized or runs in the wrong direction. In muscle-related cases, contractions may be present but too weak to move food effectively. This distinction can influence treatment decisions, but the test is invasive, uncomfortable, and only available at specialized motility centers.