1. It smells funny

If after washing and changing your sheets every week something still doesn't smell right when you're falling asleep it may indicate that you need a new mattress. When you consider the number of hours you spend in bed, it should come as no surprise that over time it collects a lot of unpleasant bacteria and fungi. If your room is damp it may also develop mold. 

2. It’s old

Modern mattresses last for about eight to ten years. Over time your mattress will lose support. It also accumulates oil, moisture, and dead skin. 

3. You feel older than you are

While support issues aren't as obvious because you can't always see them, your body will be able to tell that there may be an issue with your mattress. A lot of things that people attribute to getting older such as aches and pains can normally be credited to the age or the quality of their mattress. 

4. You see creepy crawlies      

If you see a sign of a bug in your bed it should motivate you to get a new mattress. Most people don't realize that bed bugs aren't the only thing they need to worry about. Older mattresses contain dust-mites that feed off of the dead skin that builds up in your mattress. A study conducted by Ohio State University discovered that the typical used mattress may have from 100,000 to 10 million mites in it. 

5. You don’t take care of it

In order to prolong the life of your mattress flip or rotate it a few times a year. Doing so will help the bed to wear down evenly. Higher quality mattresses do not need to be rotated. 

6. You sleep better when you’re not home

Another sign you need a new mattress is if you find that you get a better night's sleep on the couch, in a hotel bed or in a friend's bed. Your bed should be where you can get a comfortable full night's sleep. 

7. You have bad allergy or asthma symptoms

If you notice a buildup of dust mites in old mattresses this can cause allergic reactions such as a runny nose, sneezing and an itchy nose, mouth, and throat. So, if you notice that your allergies don't go away even when the pollen levels go down, it is probably time to invest in a new mattress. 

8. Your body has changed

As you get older, your body will need to be supported differently while you sleep. So, to help with pains, your bed should get firmer as you get older. This depends on the individual though, whether they sleep on their stomach, side or back. When picking a new mattress, take your pillow with you and lay on different beds in the position that you sleep every night. It's essential that you don't just test the bed by sitting or pushing on it with your hands. 

9. It’s noisy

A comfortable mattress shouldn't be loud, even when you're tossing and turning. So if you hear grinding metal or can feel displaced springs it may mean that the foundation of your mattress isn't strong anymore.