The complete guide to sleeping on your side

To sleep on your side well, keep your ear, shoulder and hip in one line with your knees slightly bent. Use a head pillow that fills the gap between your neck and shoulder, and put support between your knees. The Sleep Foundation says a small pillow between the knees may take strain off the lower back².

What good side sleeping looks like

Picture a straight line from the middle of your ear, through the point of your shoulder, to the top of your hip. In a good side position that line stays roughly level with the mattress all night. Your knees are bent a little, one on top of the other, and your arms are in front of you rather than trapped under your body.

Three things usually break that line. Your head drops toward the mattress or is pushed up toward the ceiling. Your top knee falls forward and down, which twists your pelvis. Your top shoulder rolls forward, which pulls on the upper back and the front of the shoulder.

Each fix below targets one of those breaks. You can set all five up in about 3 minutes, and none of them needs special equipment.

Fix 1: get your head pillow height right

The Sleep Foundation suggests choosing a pillow with a loft, or thickness, that matches the distance between your neck and your shoulder². That keeps your whole spine in a neutral line. For most people this is a firmer or thicker pillow than a back sleeper would choose.

A quick test takes 30 seconds. Lie on your side and ask someone to look at you from behind, or take a photo with your phone on a timer. If your nose points down toward the mattress, the pillow is too low. If your chin tilts up, it is too high.

• Narrow shoulders: start with a medium pillow and add a folded towel if needed.
• Broad shoulders: start with a high or firm pillow.
• Soft mattress: you sink further, so you often need slightly less pillow.
• Firm mattress: your shoulder sinks less, so you often need slightly more.

Fix 2: support your knees

When your top knee drops onto the mattress, the top hip rotates forward and the lower back twists. Putting a pillow between the knees keeps the top leg level with the hip. The Sleep Foundation recommends this for taking strain off the lower back².

The pillow should be thick enough that your top knee sits at the same height as your top hip. A thin cushion lets the knee keep dropping, and a very thick one pushes the leg up and can strain the outside of the hip. Our guide to sleeping with a pillow between your knees covers thickness and the three common options.

If you wake with sore hips, the knee pillow is usually the first thing to try. More detail is in how to sleep on your side without hip pain.

Fix 3: give your top arm somewhere to rest

With nothing in front of you, the top arm falls forward across your body. That drags the shoulder blade around and can leave the front of the shoulder sore by morning. Hugging a pillow gives the arm a resting place at roughly shoulder height.

The lower arm needs attention too. Lying directly on the point of the shoulder squeezes it, so bring that shoulder slightly forward so you rest more on the shoulder blade. Never sleep with the lower arm under your pillow and head for hours, which can leave the hand numb.

If one shoulder is already painful, lie on the other side where you can. Our guide on why your shoulder hurts when you sleep on your side walks through three setups.

Fix 4: stop the roll forward and back

Most people shift position many times a night. On your side, the common drift is forward onto the stomach, or back onto the back. A pillow in front of your chest and knees blocks the forward roll, and one behind your back blocks the backward roll.

For people with lower back pain, the Sleep Foundation describes side sleeping with knees slightly bent as a position that may help². A pillow behind you can make that position easier to hold. See side sleeping and lower back pain for three setups.

Fix 5: set up the room

Comfort matters as much as position. The Sleep Foundation puts the best bedroom temperature at around 65 °F (18.3 °C), with most doctors suggesting 65 to 68 °F⁶. Side sleepers who hug pillows often run warm, so a breathable cover and lighter bedding help.

• Keep the room dark and quiet, and keep the thermostat in that range if you can.
• Use a mattress that lets your shoulder and hip sink a little without sagging in the middle.
• Keep pillows where you can find them in the dark, so you do not wake fully to rearrange.

The five fixes at a glance

Which side should you sleep on

For most people, either side is fine, and switching sides through the night is normal. The Sleep Foundation notes that left-side sleeping may help people with acid reflux, while right-side sleeping may be preferred by some people with heart conditions¹. If you have heartburn, the NHS also suggests raising the head of the bed by around 10 to 20 cm and not eating within 3 or 4 hours of bed⁵.

Our guide to left side vs right side sleeping explains the evidence and the two cases where the choice matters most.

When pain is the reason you are reading this

Better positioning helps many people, but it does not replace medical advice. The NHS suggests seeing a GP if hip pain is affecting your sleep, stops normal activities, or has not improved after 2 weeks of treating it at home³. It gives similar advice for shoulder pain that has not started to feel better after 2 weeks⁴.

For back pain, the NHS advises staying active rather than staying in bed for long periods, and suggests a heat pack wrapped in a tea towel for stiffness or muscle spasms⁷. Any sudden, severe or worsening pain, or pain with fever, needs urgent care.

A sample setup for one night

1. Pick the head pillow that passed the 30 second photo test. 2. Lie on your side with knees bent about 30 to 45 degrees. 3. Slide a pillow between the knees and down to the ankles if you can, so the whole top leg is supported. 4. Hug a pillow at chest height and rest the top arm on it. 5. If you roll back in your sleep, wedge a pillow behind your back.

A crescent body pillow does steps 3 to 5 with one piece. The Cove Classic is 52 inches tip to tip, and The Cove Mini is 36 inches for smaller frames or travel. Both have a shredded memory foam fill you can adjust through an inner zip, and both come with a 100 night trial. Our size guide helps you choose by height.

Common mistakes

• Using the same flat pillow you used as a back sleeper. Side sleeping needs more height to fill the shoulder gap.
• Tucking the lower arm under the head pillow. It feels secure, but it squeezes the shoulder and can leave the hand numb.
• Lying with the top leg straight. A straight top leg slides forward and twists the pelvis just like a dropped knee.
• Curling up very tightly. A gentle bend at the hips and knees is easier on the back than knees pulled to the chest.
• Changing everything at once. If you swap the mattress, pillow and position in one night, you will not know which change helped.

Give it a week

A new position can feel odd for the first few nights, because your body is used to the old one. Try the setup for 7 nights before judging it, and change one thing at a time. If your neck still aches, adjust the head pillow first, because that is the most common cause.

Keep a simple note each morning: which side you woke on, where you felt stiff, and what you changed the night before. After a week the pattern is usually clear. If pain is getting worse rather than better, stop and speak to a GP or physiotherapist.

Guides in this series

• How to sleep on your side without hip pain
• Should you sleep with a pillow between your knees
• Why your shoulder hurts when you sleep on your side
• Left side vs right side: does it matter
• Side sleeping and lower back pain