Sleep on your left side. This is the single most effective positional change you can make to reduce heartburn at night, and the American College of Gastroenterology recommends it with what they call “unequivocal” evidence. The reason comes down to simple anatomy: when you lie on your left side, your stomach sits below the junction where it connects to your esophagus, so acid stays put. Flip to your right side, and that relationship reverses, letting acid pool right at the opening to your esophagus.
Why Your Left Side Works
Your stomach isn’t centered in your body. It curves to the left, and the point where your esophagus meets your stomach sits near the top. When you lie on your left side, gravity pulls the contents of your stomach down and away from that opening. Your esophagus ends up positioned above the pool of acid, making it much harder for anything to flow backward.
When you lie on your right side, the opposite happens. The junction between your esophagus and stomach drops into a dependent position, essentially sitting beneath the level of your stomach contents. Acid flows more easily into the esophagus, and it takes longer for your body to clear it out. This means not only more frequent reflux episodes but also longer-lasting ones, with acid sitting in contact with the esophageal lining for extended periods.
Why the Right Side Makes It Worse
It’s worth emphasizing this point because many people don’t realize that right-side sleeping actively aggravates heartburn. It’s not a neutral position. The ACG guidelines specifically note that lying right-side down increases both nighttime reflux and reflux after meals. If you currently sleep on your right side and deal with heartburn most nights, switching sides alone may bring noticeable relief.
Lying flat on your back is better than the right side but still not ideal. Without any gravitational advantage, the muscle at the base of your esophagus has to do all the work of keeping acid down on its own. For people with a weakened or relaxed lower esophageal sphincter (the cause of most chronic reflux), that’s often not enough.
Elevate Your Upper Body Too
Combining left-side sleeping with head-of-bed elevation gives you the strongest protection against nighttime reflux. Most studies use an elevation of about 20 centimeters (roughly 8 inches), which creates an incline of around 20 degrees. This height has been tested repeatedly across clinical trials and is the standard recommendation.
You have two main options for achieving this elevation:
- Bed blocks or risers: Place 8-inch blocks or risers under the two legs at the head of your bed. This tilts your entire sleeping surface at a gentle angle, keeping your body aligned naturally. It’s the most stable long-term solution.
- Wedge pillow: A foam wedge pillow elevates your entire torso from the hips up. This is a good option if you can’t modify your bed frame or share a bed with someone who doesn’t need the incline.
Regular pillows don’t work for this purpose. Stacking two or three pillows only props up your head and neck, which can actually kink your body in a way that increases abdominal pressure without creating a true incline. A wedge pillow or bed elevation lifts your whole upper body, making it genuinely harder for acid to travel upward.
For some people, using a wedge pillow consistently can reduce or eliminate the need for acid-reducing medications. That said, if you’re already on medication for reflux, positional changes work as an addition to your treatment, not a replacement.
Don’t Lie Down Too Soon After Eating
No matter which side you sleep on, timing matters. Wait at least two to three hours after eating before lying down or going to bed. Your stomach needs time to empty, and lying down while it’s still full dramatically increases the chance of reflux, even in the left-side position. This is one of the most practical changes you can make: if you tend to eat dinner at 8 and go to bed at 9, either move dinner earlier or push bedtime later.
This applies to snacking too. A late-night bowl of cereal or a handful of crackers right before bed can undo the benefit of perfect sleep positioning.
During Pregnancy
Left-side sleeping is especially useful during pregnancy, when heartburn becomes common due to hormonal changes and the growing uterus pushing the stomach upward. The NHS recommends sleeping on your left side for heartburn relief during pregnancy, and this position has the added benefit of improving blood flow to the placenta. It’s one of the few heartburn strategies during pregnancy that involves no medication at all.
Putting It All Together
The ideal nighttime setup for heartburn looks like this: finish eating two to three hours before bed, sleep on your left side, and elevate your upper body about 8 inches using a wedge pillow or bed risers. You don’t need to do all three to see improvement. Even switching from your right side to your left can make a meaningful difference on its own. But the more of these strategies you layer together, the less acid reaches your esophagus overnight, and the better you sleep.
If you wake up with heartburn in the middle of the night, check your position. Many people start on their left side and roll onto their back or right side during sleep. A body pillow placed behind you can help you stay in position. Some people also find that a wedge pillow naturally discourages rolling because the incline makes it uncomfortable to turn onto your stomach or shift to the wrong side.