Choosing a Mattress When Your Back Hurts

Start with the uncomfortable part: a mattress company is not the right source of medical advice, and we are not going to pretend a mattress fixes a back. If your back pain is severe, getting worse, or comes with numbness, weakness or changes to your bladder or bowels, that is a conversation for your GP today, not a shopping decision.

What follows is about beds, for people whose backs are stiff and sore in the morning and better an hour after getting up.

"Firm is good for your back" is the wrong lesson from a true observation

The observation is real: a collapsed, sagging mattress hurts. The conclusion people draw — so the firmer the better — does not follow. What the sagging mattress lost was support, not firmness, and replacing it with something rigid can leave the lumbar spine unsupported in a different way.

Where research has compared firmness levels, medium-firm tends to come out ahead of very firm for non-specific lower back pain. That is a population average, not a prescription, and the effect sizes are modest.

The test that costs nothing

Lie on your current mattress in the position you fall asleep in and have someone look along your spine from the side.

• On your side: the spine should run roughly straight. If your waist sags into a hollow, too soft. If there is a gap under your waist you could post a hand through, too firm.
• On your back: you should be able to slide a flat hand under the small of your back with a little resistance. Falls straight through, too firm. Cannot get it in, too soft — your hips have dropped.

Check three cheaper things first

1. The base. Take the mattress off and look. A dropped or snapped slat puts a dip in a perfectly good mattress, and gaps wider than 7 cm will ruin one over a couple of years.
2. The pillow. Upper-back and neck pain is far more often the pillow. It costs a fortieth of a mattress.
3. Where you sit. Getting dressed on the same edge every day for years puts a permanent dip exactly where you then lie.

See when to replace your mattress for the straight-edge test.

What to aim for if you do replace it

Medium to firm-medium — roughly 6 to 7 on our scale — suits most people with an achy lower back, adjusted for how you sleep and what you weigh. Front sleepers and heavier builds go firmer; side sleepers with a sore hip go softer, because the hip needs somewhere to go.

Two properties matter more than the firmness number:

• Zoned or independent support. Pocket springs and zoned latex hold the hip and the shoulder differently, which is the whole point when the two need different things. Pocket sprung range.
• A surface that lets you turn. If getting out of a hollow wakes you, you are not sleeping through the night. Latex and pocket units recover instantly; deep memory foam does not.

Give it a month

A new mattress usually feels wrong for two or three weeks because your body has adapted to the old one, and back pain in particular often gets slightly worse before it settles. Judge it at week four, which is why the trial is 100 nights and not fourteen.

Common questions

Is an orthopaedic mattress a real category?

No. "Orthopaedic" is a marketing word with no standard behind it and no medical body defining it. It usually just means firm.

Should I put a board under the mattress?

It masks a failing base and removes the ventilation underneath. Fine as a temporary measure, not as a fix.

Would a topper help?

Only if the mattress is too firm. A topper cannot rescue a sag — it follows the hollow. See toppers, pads and protectors.

None of the above is medical advice. If pain is persistent or getting worse, please talk to your GP or a physiotherapist — they can look at you, and we cannot.