Most people with GERD symptoms don’t need invasive testing right away. If you have classic heartburn and regurgitation without any alarm signs (like difficulty swallowing, unintended weight loss, or vomiting blood), the standard first step is an 8-week trial of a proton pump inhibitor (PPI) taken once daily before a meal. This medication trial essentially doubles as a diagnostic test: if your symptoms improve significantly, that response itself supports a GERD diagnosis. If symptoms persist or your doctor needs more definitive answers, several objective tests can measure acid levels, examine your esophagus, and rule out other conditions.
The PPI Trial as a First Test
American College of Gastroenterology guidelines recommend the PPI trial as the starting point for people with typical GERD symptoms. The logic is straightforward: if reducing stomach acid resolves your symptoms, acid reflux was likely the cause. You take a standard-dose PPI for eight weeks and track how you feel.
This approach catches most cases, but it’s far from perfect. A meta-analysis of 19 studies found the PPI trial has about 79% sensitivity, meaning it correctly identifies GERD roughly four out of five times. However, its specificity is only around 45%, which means more than half of people who improve on a PPI may not actually have GERD as the underlying problem. Other conditions, like functional heartburn or eosinophilic esophagitis, can also partially respond to acid suppression. So while the PPI trial is a reasonable starting point, a positive response doesn’t lock in the diagnosis, and a poor response doesn’t rule GERD out entirely.
Upper Endoscopy (EGD)
An upper endoscopy, also called an EGD, is the most common procedure used to directly examine your esophagus. A thin, flexible tube with a camera is guided down your throat while you’re sedated, so you won’t feel discomfort during the exam. The gastroenterologist looks for visible damage to the esophageal lining caused by acid exposure.
If damage is present, it’s graded using the Los Angeles classification system, which ranges from Grade A (one or more small breaks in the lining, each less than 5 mm long) to Grade D (breaks covering 75% or more of the esophageal circumference). Grades C and D are considered conclusive evidence of GERD on their own. Grade A is common even in people without significant reflux, so it’s less definitive. Your doctor can also take tissue samples during the procedure to check for complications like Barrett’s esophagus or to rule out other conditions.
Because sedation is involved, you’ll need someone to drive you home afterward. The procedure itself typically takes 15 to 20 minutes, and most people feel fine by the next day aside from mild throat soreness.
pH Monitoring
pH monitoring is the gold standard for measuring how much acid actually reaches your esophagus. There are two main versions: a catheter-based test and a wireless capsule.
The catheter-based test involves a thin tube threaded through your nose and positioned in your esophagus. You wear it for 24 hours while going about your normal routine, eating regular meals, and logging when symptoms occur. No sedation or anesthesia is needed, so you can leave the clinic immediately after placement. The tube connects to a small recording device you carry or wear on a belt. It’s not painful, but having a tube in your nose for a full day is noticeably uncomfortable for most people.
The wireless option, called the Bravo capsule, avoids the nose tube entirely. During a brief endoscopy, a tiny capsule is attached to the wall of your esophagus about 6 centimeters above where the esophagus meets the stomach. The capsule transmits pH data via radio frequency to a receiver you carry, and it records for 48 hours instead of 24, which improves accuracy. The capsule detaches on its own after a few days and passes naturally.
The key number from either test is your acid exposure time, which measures what percentage of the monitoring period your esophagus was exposed to a pH below 4 (acidic). A composite score called the DeMeester score pulls together several acid measurements into a single number, with scores above 14.7 considered abnormal.
Stopping Medications Before pH Testing
For pH monitoring to give accurate results, you need to stop taking PPIs and H2 blockers at least one week before the test. This allows your stomach to return to its normal acid production so the test reflects your actual reflux burden. Antacids and alginate-based products (like Gaviscon) can typically be used up to the night before. Your doctor’s office will give you specific instructions, but be prepared for a week of potentially worsening symptoms during this washout period.
Impedance-pH Testing
Standard pH monitoring only detects acidic reflux. Impedance-pH testing (sometimes called MII-pH) goes further by detecting all types of reflux, including weakly acidic episodes with a pH between 4 and 7, and even alkaline reflux with a pH above 7. It does this by measuring changes in electrical resistance along the esophagus, which shift when any liquid or gas moves upward from the stomach.
This test is especially useful if your symptoms persist despite PPI therapy. Since PPIs reduce acid production, reflux episodes while on medication tend to be non-acidic, and a standard pH test would miss them. Impedance testing can also show whether your symptoms actually correlate with reflux events in real time, helping distinguish true GERD from functional heartburn, where the esophagus is hypersensitive but not actually being exposed to abnormal reflux. Like catheter-based pH monitoring, it’s done without sedation and involves wearing a nasal catheter for 24 hours.
Esophageal Manometry
Manometry measures the pressure and coordination of muscle contractions in your esophagus. It’s not a direct test for acid reflux, but it plays an important role in the GERD workup for two reasons: it can identify motility problems that mimic or worsen reflux, and it’s strongly recommended before anti-reflux surgery.
During the test, a thin catheter with pressure sensors is passed through your nose into your esophagus. You’ll be asked to swallow small sips of water while the sensors map how your esophageal muscles contract and how well the valve at the bottom of your esophagus (the lower esophageal sphincter) opens and closes. The test can identify a weak sphincter, a hiatal hernia, or ineffective swallowing patterns that contribute to reflux. It also rules out major motility disorders like achalasia, which causes symptoms similar to GERD but requires completely different treatment. This matters especially before surgery, since operating on someone whose real problem is a motility disorder rather than reflux could make things worse.
No sedation is required. The procedure takes about 20 to 30 minutes, and the most uncomfortable part is the initial passage of the catheter through the nose.
Barium Swallow
A barium swallow is a simpler imaging test where you drink a chalky liquid while X-rays are taken in real time. It’s primarily used to evaluate the anatomy of your esophagus and stomach rather than to measure acid. The images can reveal hiatal hernias, narrowing (strictures), and pouches in the esophageal wall called diverticula. It won’t confirm or rule out GERD on its own, but it provides useful structural information, particularly if you’re having difficulty swallowing or if your doctor suspects a physical abnormality contributing to your symptoms.
Which Tests You’ll Actually Need
The typical path starts simple and escalates only if needed. For straightforward heartburn and regurgitation, most people begin and end with the PPI trial. If symptoms don’t respond, or if you have alarm symptoms from the start, an endoscopy is usually the next step. pH monitoring and impedance testing come into play when the diagnosis remains uncertain after endoscopy, when your esophagus looks normal but symptoms persist, or when surgery is being considered and your doctor needs objective proof of abnormal reflux. Manometry is reserved almost exclusively for the pre-surgical evaluation or when a motility disorder is suspected.
If you’re starting from scratch, the most practical first step is a conversation with your primary care doctor or a gastroenterologist about your symptoms, how long you’ve had them, and whether anything alarming is going on. That conversation will determine whether you begin with a PPI trial or skip ahead to more definitive testing.