This is why your mattress dips in the middle — and how to tell if it's safe to sleep on

A person places their hand on top of a white mattress to check for sagging
(Image credit: Getty Images)

If you're sleeping in the same bed every night, it's normal to notice that your mattress has started to dip in the middle. However, sometimes this issue can worsen over time and affect the quality of your sleep. 

Even the very best mattresses with robust support layers aren't immune to sagging over time, but how can you spot the difference between standard wear and tear and major, unfixable sagging? Here we'll explain what can cause your mattress to dip in the middle and how sleeping on a sagging mattress affects your sleep quality and back health.

Plus, we'll explain how you can fix a sagging mattress – and when to throw in the towel and replace it. If after reading this you decide that it's time to upgrade, there are plenty of mattress sales around right now to help save you money.

Why your mattress is dipping in the middle

If your mattress dips in the middle, this is known as mattress sagging and is usually a common symptoms of everyday wear and tear (there are exceptions, which we'll cover below). The main cause of mattress sagging is extended usage — remember, you're sleeping on that mattress for roughly eight hours every night — and you'll usually see that the mattress dips in areas of high usage such as the centre. 

Exposure to heat and liquids can also cause a mattress to sag. If you live in a warm climate, or your bedroom is continuously exposed to hot direct sunlight or regular liquid spills, this can speed up the sagging process. 

An old mattress leans against the side of a building

(Image credit: Getty)

That said, mattress sagging is part of the natural ageing process and you should only start to notice dips after you've slept on the mattress for a good few years. If you've had your mattress for less than six months and you've already noticed some sagging (especially if the dip measure more than 2" deep) then this is likely a manufacturing defect. If you're still within warranty (most mattress warranties last 10 years from purchase), contact the manufacturer ASAP for a replacement bed.

Is a sagging mattress safe to sleep on? 

Mattress sagging is considered minor if it isn't over 2" deep. However, if the dip is deeper than 2", sleeping on the mattress can cause issues. The firmer the mattress, the more support it gives to healthy spinal alignment, which is particularly important for back, stomach and heavyweight sleepers. 

If you sleep on your back or stomach, or weigh over 230lbs, then you'll need extra support in the hip region. If a mattress sags, this can cause your hips to sink into the mattress surface. When your hips dip, your spine becomes misaligned which leads to lower back pain. 

How to fix a mattress that dips in the middle 

If the dip in the mattress is over 2" long, but you can't afford to buy a new mattress at present, there are a few temporary solutions you can try. One of the best, cost-effective way to fix a sagging mattress is to invest in one of the best mattress toppers. Bed toppers can be used to make a mattress either softer or firmer, while some toppers come with multiple firmness options. Choose a topper that suits your needs and adds firmness and extra support. 

If you sleep alone, you could try sleeping on a different side of the bed every night to stop one side from being overused. Rotating your mattress regularly can also help to spread out the wear and tear, but this method may be ineffective if the sagging is in the dead centre of the mattress.

A woman lifts the edge of her white mattress topper placed on top of a white mattress

(Image credit: Getty Images)

Pillows are another stopgap when trying to stop the effects of sagging in a certain area, such as the dead centre, which can't be prevented or avoided by switching bed sides or rotating your mattress. Simply take one of the best pillows for dense support, and place it in the area affected by sagging. 

Some people use pieces of MDF or other wood between their bedframe and the mattress, but we don’t generally recommend this as it can become a breeding ground for bacteria, mold, mildew and dust mites. 

When to buy a new mattress 

If the sagging is significant and can’t be temporarily tempered with a topper or even temporarily fixed with pillows, check to see if it’s still covered by warranty or within the sleep trial period, then ask for an exchange. If it isn’t covered, you’ll need to replace it to prevent any damage to your back and sleep posture. 

When choosing a new mattress, invest in a durable mattress that offers sturdy support layers and excellent edge support, so you don't feel like you're sinking or dipping when you sit on the edge of the bed. The best organic mattresses tend to take a longer time to sag, as they're often made from durable latex. Latex mattresses can last up to 20 years (in contrast, memory foam, hybrid, and innerspring beds last around 8-10 years on average), but the downside is that they are very expensive.

However, there are a number of brands that offer extra-long sleep trials and warranties. Some brands offer lifetime warranties, free returns and exchanges, and one-year sleep trials, including DreamCloud and Nectar. 

Frances Daniels
Senior Sleep Staff Writer

Frances Daniels is a PPA-accredited journalist and Sleep Staff Writer at Tom's Guide with an MA in Magazine Journalism from Cardiff University. Her role includes covering mattress and sleep news and writing sleep product reviews and buyer's guides, including our Best Hybrid Mattress 2025 guide. She is hugely interested in the relationship between good sleep and overall health, interviewing a wide array of mattress and sleep experts to create well-informed articles about important topics such as nutrition, sleep disorders (from sleep apnea to night terrors), lucid dreaming, sleep hygiene, and mattress care. She is also our specialist on mattress toppers — producing mattress topper reviews and taking care of our Best Mattress Toppers 2025 guide — and takes the lead on all content related to fiberglass-free mattresses for a clean, non-toxic sleep. Outside of Tom's Guide, she has written for Ideal Home, Homes & Gardens, and Marie Claire. 

Read more
A tom's Guide tester sitting on the Nectar Luxe memory foam mattress on a bed frame in the studio
How to stop your memory foam mattress sagging in 5 easy steps
Woman sleeping on a new mattress in a brightly lit room
Keep waking up at night? Your mattress might be stopping you from sleeping through — here's why
Woman side sleeping while hugging a pillow
5 quick tips to make an old mattress feel new again
Two women sit on a Leesa Legend Hybrid Mattress in a bedroom, testing the feel of the mattress.
I test mattresses for a living and I've realized the key to a good night's sleep
A hand lifts up the 3" Latex Mattress Topper by Brooklyn Bedding to see if it needs replacing
How long do mattress toppers last? 3 key signs that they need replacing
A split screen of the cheap Siena mattress and the luxury Saatva Classic
Should you buy a cheap mattress and replace it often, or buy a luxury bed and invest in longevity?
Latest in Mattress Care
Rubber gloves hands holding a spray bottle and cleaning brush over white mattress surface
3 tricks professional mattress cleaners swear by for getting rid of urine and sweat stains
The image shows a glass bowl, a tube of toothpaste, a bottle of liquid laundry detergent and a jar of baking soda on a wooden table
I tried the viral toothpaste and warm iron DIY mattress cleaning hack for brown stains — these are my results
Koitat mattress steam cleaner on white mattress with steam coming out
I tried a mattress cleaning machine that uses steam to 'kill' bed bugs and dust mites — and I was impressed
A woman scrubbing the surface of a mattress with a blue sponge with a Sleep Week 2025 logo in the corner
5 DIY mattress cleaning jobs you should do now — avoid mold, bed bugs, allergies, and dust mites
Bed bugs or fleas on a mattress through a magnifying glass
5 things you should do now to prevent bed bugs infesting your mattress this spring
Image shows a person in blue disposable gloves pointing to bed bugs on a mattress
You might be creating the perfect conditions for bed bugs to thrive in your mattress — here's why
Latest in References
A mattress placed on a wooden floor with a Tom's Guide Sleep Week 2025 logo in the top left corner
Ditching the bed this World Sleep Day? 3 things you need before putting your mattress on the floor
A woman lies in bed with her hands covering her face, looking upset due to sleep deprivation. A Tom's Guide Sleep Week 2025 graphic, bottom left
Long-term sleep deprivation has serious health risks — but they can be reversed, says expert
Project Astra AI agent
Project Astra — everything you need to know about Google's next-gen smart glasses and new AI assistant
Two people place a covered mattress in a van to move it to a new house
Which mattress brands offer old mattress removal?
Blonde woman laying on Brooklyn Bedding CopperFlex mattress in bedroom with wooden floor, wooden bed base and two bedside tables
What is copper in a mattress and does your cooling mattress need it?
A couple laying on Bear Elite Hybrid mattress with Celliant in bedroom with black pattern rug, grey headboard and black bedside tables with lamps
What is Celliant and does your cooling mattress need it?