Lie on your left side. This is the single most effective sleeping position for heartburn, and the evidence behind it is strong enough that the American College of Gastroenterology lists it as a recommended lifestyle change for managing reflux. The reason comes down to anatomy: your stomach naturally curves to the left, so when you lie on that side, your esophagus sits above the level of your stomach contents, making it harder for acid to travel upward.
Why the Left Side Works
Your stomach isn’t a symmetrical pouch. It curves to the left side of your body, and the opening where your esophagus connects to your stomach sits toward the right. When you lie on your left side, that connection point ends up positioned above the pool of stomach acid and food below it. Gravity keeps everything in the stomach where it belongs.
A study that simultaneously tracked sleep position and esophageal acid levels found that acid exposure time in the left-side position was dramatically lower (median 0.0%) compared to the right side (median 1.2%) and lying on your back (median 0.6%). More importantly, when acid did reach the esophagus, it cleared much faster on the left side: a median of 35 seconds, versus 90 seconds on the right side and 76 seconds on your back. That’s roughly two and a half times faster acid clearance just from switching sides.
Why the Right Side Makes It Worse
When you flip to your right side, the anatomy works against you. Your esophagus drops below the junction with your stomach, essentially sitting underneath the pool of acid. This makes it easy for stomach contents to flow back up into the esophagus and much harder for your body to clear them once they do. The ACG guidelines note that right-side sleeping increases reflux both at night and after meals, and they specifically advise patients to avoid it.
If you tend to roll onto your right side during the night, some people use a body pillow or a positioning wedge behind their back to help stay on the left. It can take a few nights to adjust, but the difference in symptoms is often noticeable quickly.
Elevating Your Upper Body Adds More Relief
Combining left-side sleeping with upper body elevation gives you the most protection against nighttime reflux. The goal is to raise the entire upper half of your torso, not just your head. Most wedge pillows designed for acid reflux use a 30- to 45-degree angle and lift the head between 6 and 12 inches. Alternatively, you can place 6- to 8-inch blocks or risers under the legs at the head of your bed. Multiple clinical trials have used 20 to 28 centimeter (roughly 8 to 11 inch) elevations and found consistent improvement in nighttime symptoms and acid exposure.
One important detail: stacking regular pillows under your head doesn’t work the same way. Propping up just your head and neck can actually bend your body at the waist, increasing pressure on your abdomen and potentially making reflux worse. The elevation needs to be gradual, from your waist up, so your whole torso is on an incline.
Timing Your Last Meal Matters Too
Even the best sleeping position can only do so much if you lie down on a full stomach. The standard recommendation is to wait at least three hours between your last meal and going to bed. Research backs this up significantly: people who ate dinner less than three hours before bed were over seven times more likely to experience reflux symptoms compared to those who waited four hours or more. If you tend to eat late, this single change can be as impactful as switching your sleep position.
Sleeping Position During Pregnancy
Heartburn is extremely common during pregnancy, especially in the second and third trimesters, as the growing uterus pushes upward on the stomach. Left-side sleeping is already the preferred position in pregnancy for circulation reasons, so it does double duty by also reducing reflux. A 4- to 6-inch incline for the upper body adds further protection.
As with anyone else, pregnant women should avoid using a stack of pillows that bends the body at the abdomen. A full-length wedge or bed risers keeps the torso on a smooth incline without adding pressure to the stomach. Avoiding lying flat or bending over shortly after eating also helps keep symptoms manageable.
Quick Comparison of Sleep Positions
- Left side: Lowest acid exposure, fastest acid clearance (median 35 seconds). Recommended by gastroenterology guidelines.
- Back (supine): Moderate acid exposure, slower clearance (median 76 seconds). Better than the right side but worse than the left.
- Right side: Highest acid exposure, slowest clearance (median 90 seconds). Actively worsens reflux by positioning the esophagus below stomach contents.
- Stomach (prone): Not well studied for reflux specifically, but compresses the abdomen and is generally not recommended for heartburn.
If you only make one change tonight, roll onto your left side. If you want maximum relief, combine it with a gradual upper-body incline and a three-hour gap between dinner and bedtime.