Side Sleeping
The most common adult sleeping position, and the one most sensitive to pillow height. Here is what changes when you lie on your side, and what to adjust first.
By the Somnora editorial team · Last updated September 1, 2026
What changes when you roll onto your side
Your shoulder becomes the load-bearing point. The head is now suspended above the mattress by roughly the width of that shoulder, and the pillow has to fill the difference. On your back, the same pillow would be far too tall.
Getting the height right
- Lie on your side on your own mattress, with your usual pillow.
- Ask someone to look at you from behind, or take a photo — the aim is a roughly straight line from head to mid-back.
- If your head tips down toward the mattress, you need more loft. If it is pushed up toward the ceiling, you need less.
- Change one variable at a time and give each change a few nights.
Full detail in the pillow height guide, and product-level options in pillows for side sleepers.
Shoulder pressure and arm position
Side sleepers concentrate weight on one shoulder. A softer mattress surface lets the shoulder sink, which reduces pressure but also reduces the loft you need — the two adjustments interact. Tucking an arm under the pillow is often a sign the pillow is too low.
Small adjustments worth trying
- A pillow between the knees, which many side sleepers find keeps the hips more comfortable.
- A firmer pillow rather than a taller one if your current pillow flattens by morning — see firm pillows.
- A contoured design if you want the height difference built in rather than adjusted.
Is side sleeping a good position?
It is the most common adult sleeping position and works well for many people. Comfort depends far more on whether your pillow and mattress suit your body than on the position itself.
Which side should I sleep on?
For most people it is a matter of preference. Some conditions have position-specific guidance from clinicians — that is a conversation for a qualified healthcare professional rather than a pillow site.
Why does my arm go numb when I sleep on my side?
It is often related to pressure and arm position, and a pillow that is too low can encourage burrowing your arm under your head. Persistent or frequent numbness should be assessed by a healthcare professional.