Can you get food poisoning from out of date milk?

November 28, 2025 •

3 min read

According to research from the National Institutes of Health, some unopened, refrigerated milk can be safe days past its listed date, but proper storage is vital. So, can you get food poisoning from out of date milk? The clear answer is yes, though the risk level varies based on several key factors related to spoilage and bacteria.

Quick Summary

Consuming spoiled, out-of-date milk can cause food poisoning, with symptoms like nausea and stomach pain. The risk is determined by proper storage, refrigeration, and sensory signs of bacterial growth, not just the printed date.

Key Points

Yes, it's possible: Consuming spoiled milk can cause food poisoning due to bacterial overgrowth that occurs over time.
Rely on your senses: The best way to know if milk is safe is to check for a sour smell, clumpy texture, or any visible changes rather than strictly relying on the date.
Storage is critical: Improper temperature control is the primary cause of accelerated spoilage and increases the risk of bacterial contamination.
Expiration dates are not definitive: The "sell-by" date is a freshness indicator, not an expiration date, and milk can be good for days past this if unopened and properly stored.
Know the symptoms: Symptoms of milk-related food poisoning typically include nausea, vomiting, stomach cramps, and diarrhea.
Raw milk has higher risk: Raw, unpasteurized milk carries a much higher risk of containing harmful pathogens than pasteurized milk.
When in doubt, throw it out: If you are unsure about the safety of your milk, the small cost of a new carton is far less than the potential risk to your health.

While a sip of slightly sour milk is unlikely to cause serious harm, drinking a moderate to large amount of spoiled milk can definitely cause food poisoning. This is because even after pasteurization, a small number of bacteria remain, and these organisms will multiply over time, especially if not stored properly. This process eventually causes the milk to spoil and potentially contain harmful toxins from bacterial growth.

The Science Behind Milk Spoilage

Milk is a nutrient-rich environment, which unfortunately makes it an ideal breeding ground for bacteria. Pasteurized milk has been heat-treated to kill most of the harmful pathogens, but not all of them. Over time, lactic acid bacteria continue to grow, breaking down the lactose and producing lactic acid, which causes the milk to become sour. Other spoilage bacteria and, in some cases, harmful pathogens like E. coli or Salmonella, can also multiply, posing a serious health risk.

The Difference Between 'Best By' and 'Bad'

It's important to understand what the date on your milk carton actually means. Most milk is labeled with a “sell-by” or “best-by” date, which is an indicator of peak freshness and quality, not necessarily a hard-and-fast safety deadline. A study found that an unopened, properly refrigerated carton of milk could be safe for up to a week past this date. However, once opened, the milk's exposure to air and other contaminants accelerates bacterial growth, and its shelf life shortens dramatically. Therefore, relying on your senses is far more reliable than the printed date.

Risk Factors for Food Poisoning

Several factors can increase the risk of getting sick from expired milk. Poor temperature control is a primary culprit. Leaving milk out at room temperature for more than two hours significantly increases the risk of foodborne illness. The type of milk also plays a role. Raw, unpasteurized milk has not undergone the heat treatment process and naturally contains more bacteria, including potentially dangerous pathogens, giving it a much shorter and riskier shelf life. Higher fat content in milk can also affect spoilage, as one study noted increased bacterial growth rates in higher fat milk.

Signs That Your Milk Has Spoiled

Sour smell: A strong, pungent, or sour odor is a definitive sign of spoilage due to the activity of lactic acid bacteria.
Change in texture: Spoiled milk will often become thick, clumpy, or curdled, indicating bacterial activity that alters the protein structure.
Discoloration: While subtle, spoiled milk may appear yellowish rather than a pure white.
Mold: Any sign of mold on the surface is a clear indicator that the milk is no longer safe for consumption.

A Comparison of Milk Types and Spoilage Risk


Feature	Pasteurized Milk	Raw (Unpasteurized) Milk
Processing	Heat-treated to kill most pathogens.	Untreated, contains natural bacteria.
Pathogen Risk	Low, if properly handled and refrigerated.	High, may contain harmful pathogens.
Shelf Life	Longer (5-7 days after sell-by, if unopened).	Much shorter, highly susceptible to rapid spoilage.
Storage Importance	Critical; temperature abuse accelerates spoilage.	Extremely critical due to lack of treatment.
Storage Conditions	Constant refrigeration below 40°F (4°C).	Strict refrigeration and quick consumption needed.

Symptoms of Food Poisoning from Spoiled Milk

If you have consumed spoiled milk, symptoms typically appear within a few hours to a day and can range in severity.

Mild to Moderate Symptoms:
- Nausea
- Vomiting
- Stomach pain or cramps
- Diarrhea
Severe Symptoms:
- Bloody diarrhea
- High fever (over 102°F)
- Diarrhea lasting more than three days
- Signs of dehydration (e.g., decreased urination, dizziness).

What to Do If You've Consumed Spoiled Milk

If you experience only mild symptoms, rest and stay hydrated with clear fluids. If symptoms persist, worsen, or if you begin experiencing signs of dehydration or severe illness, contact a healthcare provider. Always seek immediate medical attention if you suspect you have consumed raw milk that has made you ill.

Conclusion: Don't Take the Risk

When it comes to milk, the expiration date is a useful guide, but your senses are the ultimate authority. While a controlled study showed unopened milk might last past its date, once opened, the risk of contamination and accelerated spoilage increases. The potential for getting food poisoning from out-of-date milk is real, especially with improper storage. Always store milk in the coldest part of your refrigerator and, if there's any doubt about its freshness—a sour smell, curdled texture, or strange appearance—it’s best to err on the side of caution and dispose of it to protect your health. For more information on preventing foodborne illness, visit the CDC's official guidelines.

Frequently Asked Questions

Food poisoning is caused by harmful bacteria or toxins, leading to symptoms like vomiting and diarrhea. Normal stomach upset might result from consuming something your body finds distasteful, but without the pathogenic load, the effects are typically less severe and shorter-lived.

No, cooking spoiled milk does not make it safe. While heat kills some bacteria, many food poisoning bacteria produce heat-stable toxins that are not destroyed by cooking and can still make you sick.

To extend milk's shelf life, store it at a consistent temperature below 40°F (4°C) in the back of the refrigerator, not in the door. Ensure the cap is tightly sealed after each use to minimize exposure to air and other contaminants.

Some baking recipes specifically call for sour milk, which traditionally referred to naturally soured milk from lactic acid bacteria. However, it's safer to create a substitute by adding vinegar or lemon juice to fresh milk to avoid any risk of pathogenic bacteria from spoiled milk.

If your unopened milk is only slightly past its 'sell-by' date and shows no sensory signs of spoilage (bad smell, clumps), it is likely safe to consume, especially if it has been stored properly. Once opened, however, its safety duration is shorter.

Bacteria like E. coli, Salmonella, and Campylobacter are common causes of foodborne illness and can be present in milk, especially if it is raw or becomes contaminated after pasteurization.

While rare, severe food poisoning from any source, including milk, can be life-threatening, especially for vulnerable populations like young children, the elderly, and those with weakened immune systems. Contamination with serious pathogens is the primary risk.