How Long Can Milk Sit Out?

It's OK to leave your milk out intermittently. For example, if you leave it out while you're making pancakes and return it to the fridge as soon as you're done, you'll be fine. But usually, you don't want to leave it out for more than the recommended two hours, or one hour when it's in an environment over 90 degrees F. These are in the general safe window but can vary depending on the situation. 

Nicole Martin, PhD, assistant research professor in dairy foods microbiology at Cornell University, warns that “If the milk is in a smaller container (e.g., a quart) versus a larger container (e.g., a gallon), the product will warm up faster, and this can allow bacteria to grow a little faster.”

Conversely, some milks are less risky to leave out for long periods. Martin explains ultra-pasteurized milk, for instance, undergoes a higher heat treatment that kills both the pathogens and spoilage bacteria, so it’s not as sensitive to temperature differences.

No matter the milk type or container size, it’s best to play it safe. “Only take milk out of the refrigerator to use it and then put it right back to avoid light exposure and warm temperatures,”

This is because “if milk is left out too long at one time, or is often left out for shorter periods of time (e.g., during a meal), the results may be that it will not last the full expected shelf-life, or the date indicated on the container,” Martin says. “Spoilage may make the milk smell different, look different or taste different than it should.”

And the impact doesn’t stop there. “Milk is sensitive to light, so leaving milk out may result in an off flavor called oxidation,” she says.

So overall, leaving milk out too long can make it unsafe to drink, despite the pasteurization process. Because once milk is spoiled, it’s spoiled.

That’s why it’s important to store your milk properly.

The Best Ways to Store Your Milk and Preserve Freshness

Milk is pasteurized to kill bacteria that could potentially cause health risks. Even so, it is not safe to leave pasteurized milk unrefrigerated for an extended time, because of this, milk must be properly stored. Promptly returning your milk to the fridge after you take it out is a great place to start when it comes to storing the beverage. And if you want to maximize the freshness of your inventory, these other best practices will help you take things up a notch.

●      Grab milk last at the grocery store. That way, it’s out for less time and stays as cool as possible between the dairy case and your refrigerator.

●      Set your refrigerator between 36-38 degrees F. “Milk should be kept [stored] below 40 degrees F, but keeping it a little colder will keep it fresher for longer,” Martin says.

●      Keep your milk in the back/colder part of the refrigerator. As Martin warns, storing milk in the fridge door can cause its temperature to fluctuate more every time you open the fridge. This may make the milk spoil faster than if kept in the back.

●      Store milk in a container you won’t drink out of. This can be the original carton or jug, or a glass container at home. But unless you’re finishing the last of your milk, it’s best not to drink it right out of the container. “This can introduce bacteria that can accelerate spoilage,” Martin says.

●      Freeze milk you won’t use before its expiration date. This will prevent bacteria from growing until you thaw the milk, and help you avoid food waste.

These efforts may seem small, but they can have a big impact. Following these simple guidelines can keep your milk as fresh as possible and help you avoid throwing out spoiled milk. For more information on food safety, visit FoodSafety.gov.

What Happens If You Drink Spoiled Milk

As we’ve learned, when you leave milk out too long, it can start to spoil — and more. Drinking spoiled milk can lead to stomach discomforts like nausea, vomiting, and diarrhea, as it may contain harmful bacteria that grow when the milk goes bad. The sour taste and curdling are signs of bacterial growth, which can cause digestive upset when consumed. 

While not everyone may experience symptoms, it’s always best to avoid drinking spoiled milk as to prevent foodborne illness and digestive issues. If you suspect you’ve ingested spoiled milk and feel unwell, it's important to stay hydrated and seek medical attention if necessary.

How To Know If Milk Is Bad

To know if milk is bad, check for a sour odor, curdling, clumping, and/or a rancid taste. If the milk appears thicker than usual or has an unusual consistency, it may have spoiled. While the expiration or "sell by" date can provide a general guideline, it’s important to trust your senses—if the milk smells or tastes sour, it’s time to discard it. Always use caution and avoid consuming milk that shows any of these signs of spoilage to prevent foodborne illness.

How Long Is Milk Good After Sell By Date

Milk can typically be good for 5 to 7 days after the "sell by" date if stored properly in the refrigerator at or below 40°F (4°C). However, its freshness depends on how it's been handled and stored, so always check for signs of spoilage, such as sour odor, curdling, or changes in texture. While the "sell by" date is a helpful guideline, it's not an exact measure of milk's safety, so trusting your senses—like smell and taste—will give you the best indication of whether milk is still good to drink.

The expiration date of milk is the final date the manufacturer guarantees the milk will be at its best quality, and it’s typically safer to follow than the "sell by" date when determining freshness. Like with the "sell by" date, rely on your senses to decide whether the milk is still good.

Why Milk Needs to Be Refrigerated

Milk isn’t only refrigerated because it tastes great cold. Similar to other perishable foods, the cold temperature helps delay growth of bacteria that could otherwise spoil milk.

From the farm to the dairy processing plant and then to the store, milk is strictly monitored to ensure the highest level of freshness, purity and great taste. As a result of these stringent food safety standards, milk is among the safest foods and dairy products in the world.

It starts on the farm. Our nation’s dairy farms are committed to producing high-quality milk, while maintaining proper animal care and environmental practices. That means farmers provide safe, comfortable housing for their animals, nutritious feed, regular veterinary care, and sanitary milking conditions. Once cows are milked, several milk tests are done. For example, milk is tested for antibiotics on the farm and once again when milk is delivered to the plant. Any milk that tests positive cannot be sold to the public.

At the processing plant, milk goes through several steps, including pasteurization and homogenization. 

“Most milk in the United States is pasteurized, or heated, using a very gentle treatment that is only designed to kill pathogens, the bacteria that can make you sick,” explains Nicole Martin, PhD, assistant research professor in dairy foods microbiology at Cornell University. “The result is there are only a few bacteria in the milk, even after pasteurization, that can eventually cause the milk to spoil over time. Refrigeration slows down the growth of these spoilage bacteria so you can enjoy your milk for longer.”

This doesn’t mean you’re ruining your milk every time you take it out to pour a glass. But it does mean you play a role in food safety, too. For example, when at the store, pick up your milk last so it stays as cool as possible. Place milk in the fridge as soon as you get home. There are several ways you can make sure your milk stays as fresh as possible.