Sleeping on your left side is the best position for acid reflux. This isn’t a marginal difference or a matter of personal preference. The American College of Gastroenterology calls the evidence “unequivocal” that left-side sleeping reduces reflux symptoms, making it one of the strongest lifestyle recommendations for nighttime heartburn.
Why the Left Side Works
The answer comes down to where your stomach sits in your body. Your stomach curves naturally to the left, and the junction where your esophagus meets your stomach sits higher than the bulk of your stomach’s contents when you lie on your left side. Think of it like tilting a bottle so the opening points upward: gravity keeps the liquid away from the cap. When you sleep on your left, your esophagus sits above the pool of acid, making it harder for stomach contents to wash back up.
Flip to your right side and the geometry reverses. That junction between your esophagus and stomach drops into a lower position relative to the acid pool, essentially putting the “cap” of the bottle below the liquid line. This is why right-side sleeping consistently increases both the number of reflux episodes and how long acid lingers in the esophagus. The ACG specifically advises patients to avoid sleeping on the right side.
How Other Positions Compare
Sleeping on your back also tends to make reflux worse. When you’re flat on your back, your stomach contents spread out evenly and sit right at the level of the esophageal opening, making it easy for acid to creep upward. Some people find back sleeping tolerable if they elevate their upper body, but the position itself doesn’t offer the gravitational advantage that left-side sleeping does.
Stomach sleeping can reduce reflux for some people by letting gravity pull acid away from the esophagus, but it introduces other problems. The pressure on your chest and abdomen can be uncomfortable, and the neck twist required to breathe puts strain on your spine. For most people, left-side sleeping is the more practical and sustainable option.
Elevating Your Head Helps Too
The ACG also suggests raising the head of your bed for nighttime reflux, though they note the evidence here is weaker than for left-side sleeping. The idea is straightforward: a slight incline lets gravity work in your favor by keeping acid in the lower part of your stomach.
You can achieve this a few ways. Bed risers or blocks under the headboard legs tilt your entire body on a gentle slope, which keeps your spine aligned. A wedge pillow does something similar by angling your torso upward from the waist. Simply stacking regular pillows under your head is less effective because it bends you at the neck rather than elevating your whole upper body, and can actually increase abdominal pressure.
Combining left-side sleeping with a slight incline is likely your best setup, since you’re using two separate mechanisms to keep acid where it belongs.
Timing Your Last Meal Matters
Position is only half the equation. The standard recommendation is to stop eating at least three hours before you go to bed. A study on dinner-to-bed timing found that this three-hour window gives your stomach enough time to empty most of its contents, so there’s simply less acid available to reflux when you lie down. Eating a large or fatty meal right before bed can overwhelm even the best sleeping position.
If you’re someone who snacks late, even shifting that window by an hour can make a noticeable difference. The goal is to go to bed with a relatively empty stomach rather than one that’s still actively digesting.
Staying on Your Left Side All Night
The obvious challenge is that you can’t control what your body does while you’re asleep. Most people shift positions multiple times per night. A few strategies can help you stay put longer.
- Body pillow: Placing a full-length pillow behind your back creates a barrier that discourages rolling onto your back or right side.
- Wedge pillow with a left-side setup: Some wedge pillows are designed with a slight lateral tilt that makes left-side sleeping more natural and comfortable.
- Tennis ball trick: Placing a tennis ball in a pocket sewn onto the back or right side of a sleep shirt creates enough discomfort to nudge you back to your left side without fully waking you.
You don’t need to stay perfectly on your left side for eight straight hours to see a benefit. Even spending most of the night in that position, particularly during the first few hours after going to bed when reflux is most likely, can significantly reduce symptoms.
Acid Reflux and Pregnancy
Heartburn is extremely common during pregnancy, especially in the second and third trimesters. Left-side sleeping is already the standard recommendation for pregnant women for circulatory reasons, so it does double duty by also reducing reflux. Cleveland Clinic recommends pregnant women wait at least two to three hours after eating before lying down and keep the head of the bed elevated. These are the same principles that apply to anyone with reflux, just with the added motivation that many heartburn medications are best avoided during pregnancy.