Does Miso Soup Go Bad? Here’s How you Can Tell

A bowl of miso soup with tofu and chopsticks off to the side.

Miso soup is a great tasting and very healthy food. It contains miso paste, which is known for lasting a very long time without going bad, and because of this you may be wondering, does miso soup go bad? Or can it also last up to a year in the right conditions?

Miso soup does go bad. If the soup is kept in the fridge, it can last for 2 to 3 days before it goes bad, but it can go bad if kept for longer. So, do not treat miso soup the same way that you would treat miso paste (which may last up to a year when kept in the fridge), assuming it will last long. 

What exactly goes into miso soup that can cause it to go off when miso paste on its own can last so long then? What makes this soup have such a short timeframe for when it is suitable to eat it? Let’s take a closer look.

Does Miso Soup Go Bad?

Miso soup can go bad, and it could happen in a relatively short period of time. The reason so many people often think that miso soup won’t go bad is because of the longevity of the miso paste itself.

Miso paste is a fermented product, and it also contains a lot of salt, making it a very well-preserved product that can last up to a year in the refrigerator. Miso paste hardly ever goes off, making it an easy product to store for long periods of time. If you’re interested in making your own miso soup, I like this miso from Amazon.

However, this does not mean that miso soup will be the same. Remember that miso soup is still a fresh product that contains other ingredients in it that can still go off quickly.

The fresh ingredients that are used in miso soup can vary, but alongside miso paste, often other products that are used in miso soup include seaweed, tofu, and fresh vegetables.

Due to the fact that this soup also contains miso paste, a product that is so high in probiotics, it actually leaves the soup at a greater risk of going bad quicker due to the live bacteria in the prepared soup.

How Long Until Miso Soup Goes Bad?

Miso soup will generally only last for a few days after it has been made before it will go bad. How quickly it goes off will also depend on how you store the soup.

Once you have finished eating your miso soup and you are ready to pack the left-over soup away, you should start by allowing the soup to cool down entirely. This can sometimes take hours, but have patience because it is important.

Once the soup is completely cooled down, you will need to put it in an airtight container and store it in the fridge.

Miso soup that is stored in the fridge will usually last two to three days before going bad – this is a relatively short amount of time to be able to store something in the fridge before it goes off, but as was discussed, miso soup has live bacteria in it.

DID YOU KNOW? The live bacteria in miso soup is incredibly good for you and for your gut health as it is so rich in probiotics. This soup also contains many other minerals and vitamins that your body needs, such as vitamin K, vitamin E, and folic acid, to name a few.

Fresh food products that do not have preservatives in them do unfortunately go bad quicker than foods that are not fresh and that are full of preservatives.

So, even though it may feel frustrating that your miso soup would go bad so quickly, just remember that it is actually a good thing, as it indicates that the miso soup is a fresh and high-quality food – and sometimes the price you pay for fresh and high-quality food is that you will not be able to keep it as long.

A top view of miso soup with tofu in it.
The benefits of having miso soup will usually outweigh the frustration of it going off quickly.

How Do You Know if Miso Soup Has Gone Bad?

There are a few different key ways that you will know whether or not your miso soup has gone bad or if it is still fine to eat. However, if you are ever unsure of whether or not it has gone bad, it’s best not to eat it.

Eating miso soup that has gone bad can give you food poisoning, or at the very least, cause some intestinal distress. So when it comes to old miso soup, if you are unsure it’s best to play it safe rather than be sorry that you ate it.

Some of the signs to look out for when it comes to telling if your miso soup has gone bad include:

  • A bad smell – miso soup has a very unique smell, but if this smell ever changes and develops a pungent or sour smell, throw it away as there is a high chance it has gone bad.
  • Mold – this should be a fairly obvious one; however, if there is ever any mold that has started to grow on your miso soup it is a good indication that the soup has gone bad. Do not try and scrape the mold off and eat the soup, just throw the soup away.
  • If it’s older than a week – with miso soup only lasting about 2 to 3 days in the fridge before going off, if you have some left-over miso soup in your fridge from last week do not eat it. There is a very high chance that it will no longer be suitable for consumption.

If there are ever other abnormalities in your leftover miso soup, such as discoloration or anything else, it’s better to discard the soup than take the risk.

How Long Does Miso Soup Last Out of The Fridge?

Leaving miso soup out of the fridge is a risky thing to do. Miso soup only lasts two to three days in the fridge, so without being kept in a cool environment to help it keep fresh for as long as possible, chances are that your soup will not stay edible for very long.

The exception to this, however, is the possibility of leaving your soup out on the stove overnight.

If you are wanting to cook your soup a day in advance for whatever reason, you can do the following:

  • Prepare and make your miso soup just as you normally would.
  • Once the soup is finished, put the lid on your pot, and turn the stove off.
  • Leave your soup in the pot with the lid on overnight (once the oven plate has completely cooled down, you can even wrap a kitchen tea towel around the pot and put one over the lid to keep as much warmth in as possible.)
  • When you wake up the next morning, warm the soup up again on medium heat for around 10 minutes to make sure it has warmed up all the way through, and you can then serve your soup when ready.

This is not a fail-proof way to always ensure that your soup will last well being left out overnight, so always use discretion before eating the soup to ensure that it did not go bad overnight. 

A pile of miso on a small plate.
Miso can last up to a year in the refrigerator, but it’s not the same for soup


Miso soup can definitely go bad, and it can actually happen in a very short time frame. It’s always important to exercise caution and check that your left-over miso soup is still okay to eat before you dive right in come lunchtime.

If you are ever unsure as to whether your soup is still fine to eat, first look for the obvious signs of the soup being off, but if you have done the checks and you are still just completely unsure if it is fine – give it a pass.

Old miso soup that has gone bad can give you food poisoning as well as just a bad case of intestinal distress if consumed, so always play it safe when it comes to eating miso soup after a few days. If it is not clear that it is still fine to eat, just skip it.

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