Lying on your left side is generally the better choice when you’re feeling nauseous. This position keeps your stomach below your esophagus, which reduces the chance of acid and stomach contents creeping upward and making nausea worse. The right side does the opposite, positioning your stomach above the opening to your esophagus and encouraging reflux.
Why the Left Side Works
Your stomach isn’t centered in your body. It curves to the left, and the junction where your esophagus meets your stomach sits at a specific angle. When you lie on your left side, gravity pulls the contents of your stomach down and away from that junction. Your esophagus ends up sitting higher than your stomach, so there’s a natural barrier against anything flowing back up.
When you lie on your right side, the geometry flips. Your stomach sits above the esophageal opening, and its contents pool closer to the valve between the stomach and esophagus. If that valve is relaxed (which is common during sleep or when you’re feeling unwell), acid and partially digested food can flow back into the esophagus more easily. A systematic review and meta-analysis found that right-side sleeping induced more heartburn and reflux episodes than any other position, while left-side sleeping significantly reduced them. That reflux is one of the most common drivers of nausea, especially when you’re lying down.
Elevating Your Head Helps Too
Position alone doesn’t do all the work. Raising your head and upper body by about 20 centimeters (roughly 8 inches) adds another layer of gravity working in your favor. Clinical trials have tested this using wedge-shaped pillows and blocks under the head of the bed, with elevation angles around 20 degrees. Both approaches reduced reflux symptoms compared to lying flat. You don’t need anything fancy: a firm wedge pillow or an extra pillow that keeps your torso at a gentle incline can make a real difference. Stacking soft pillows under just your head can kink your neck and actually increase abdominal pressure, so aim to elevate from the waist up.
Combining left-side lying with a slight head elevation is the most effective setup for keeping stomach contents where they belong.
If You’re Actively Vomiting
When nausea crosses over into vomiting, preventing choking becomes more important than preventing reflux. The key is making sure vomit can drain out of your mouth rather than back into your airway. Lying on either side in a recovery position (body tilted slightly forward, mouth angled toward the ground) accomplishes this. Emergency guidelines recommend this side-lying posture for anyone who is vomiting or has a reduced level of consciousness, because people found lying on their backs after vomiting have significantly higher rates of aspiration pneumonia.
In this situation, either side works. The priority is simply not being flat on your back. If you’re alert and just managing waves of nausea with occasional vomiting, the left side still gives you the combined benefit of reflux prevention and airway safety.
Nausea During Pregnancy
Many physicians advise pregnant women to sleep on their left side, and this recommendation overlaps nicely with nausea relief. The reasoning during pregnancy goes beyond digestion: as the uterus grows, it can compress major blood vessels when you lie on your back or right side, potentially reducing blood flow. Left-side lying takes that pressure off.
That said, an NIH-funded study found that sleeping position during early and mid pregnancy (through about 30 weeks) did not appear to increase the risk of complications like stillbirth or low birth weight regardless of position. The researchers noted this should reassure pregnant women who have trouble staying on their left side all night or who shift positions during sleep. For nausea specifically, the left side still offers the same gravity advantage for keeping stomach acid down, which can help with the reflux component of morning sickness.
When Position Alone Won’t Help
Not all nausea comes from your stomach. If your nausea is triggered by specific head movements, like rolling over in bed, getting up, or looking upward, the cause may be vestibular rather than digestive. A condition called benign paroxysmal positional vertigo (BPPV) occurs when tiny crystals in your inner ear shift out of place, sending false motion signals to your brain. With BPPV, the nausea is triggered by the position change itself, not by which side you end up on. Lying still on your left side may reduce reflux-related nausea layered on top, but it won’t address the spinning sensation. BPPV is treated with specific head-repositioning maneuvers that a clinician can guide you through.
Nausea from motion sickness, migraines, or medications also won’t respond to side positioning the same way reflux-driven nausea does. In those cases, lying on your left side with your head slightly elevated is still a reasonable default because it avoids making things worse, but the nausea itself has a different mechanism that positioning alone can’t fix.