Pasteurized milk sold in stores is one of the most heavily tested and regulated foods in the supply chain, and it is safe to drink. The pasteurization process eliminates dangerous bacteria without meaningfully changing milk’s nutritional value, and routine testing catches contaminants like antibiotics before milk reaches shelves. That said, how you store milk at home, whether you choose raw milk, and how your body handles lactose all affect whether a glass of milk is truly safe for you.
What Pasteurization Actually Does
Raw milk can carry a long list of harmful bacteria: E. coli O157:H7, Salmonella, Campylobacter, Listeria, Staphylococcus aureus, and even the organism that causes tuberculosis. Pasteurization, which heats milk to a specific temperature for a set time, is the only method that achieves complete elimination of these living pathogens. It does this without any significant impact on the vitamins, minerals, or protein content of the milk.
Every carton of milk you buy at a grocery store in the U.S. has been pasteurized unless it’s explicitly labeled “raw.” This single step is the reason commercial milk is overwhelmingly safe.
The Real Risk of Raw Milk
Raw, unpasteurized milk is a different story entirely. Only about 3.2% of the U.S. population drinks it, yet raw dairy products account for 96% of all illnesses caused by contaminated dairy. A CDC analysis covering 2009 through 2014 found that unpasteurized dairy causes roughly 840 times more illnesses and 45 times more hospitalizations than pasteurized products. Most of those illnesses come from Salmonella and Campylobacter infections, which can cause severe diarrhea, fever, and cramping lasting a week or more.
Claims that raw milk is more nutritious or builds immunity are not supported by evidence. The FDA is direct on this point: pasteurization kills pathogens without reducing nutritional quality. For children, the elderly, pregnant women, and anyone with a weakened immune system, raw milk poses an especially serious risk because infections like Listeria can be life-threatening in these groups.
Hormones and Antibiotics in Milk
Many people worry about hormones in conventional milk. Some dairy cows are treated with a synthetic growth hormone (rBGH) to increase milk production. Milk from treated cows does not contain significantly higher levels of the growth hormone itself, but it does have elevated levels of a protein called IGF-1, which is involved in cell growth. Whether those slightly higher IGF-1 levels in milk pose a health concern remains debated, but it’s worth knowing that many major dairy brands have voluntarily moved away from rBGH use, and organic milk prohibits it entirely.
Antibiotic contamination is a more concrete concern, but testing data is reassuring. In fiscal year 2019, the FDA’s national drug residue program tested nearly 4 million milk samples. The positive rate for antibiotic residues was remarkably low: 0.009% of bulk tanker samples and just 0.003% of pasteurized retail milk. Any tanker that tests positive is rejected before it enters the supply chain. In practice, the milk you buy has an extremely small chance of containing antibiotic residues.
Other Contaminants: What Gets Monitored
Milk can also pick up environmental contaminants through cattle feed. The one regulators watch most closely is aflatoxin M1, a byproduct that ends up in milk when cows eat grain contaminated with certain molds. The FDA set an action limit of 0.5 parts per billion for aflatoxin M1 in fluid milk back in 1977, and milk exceeding that threshold is subject to enforcement action. Routine monitoring keeps levels well below this ceiling in commercial milk.
How Long Milk Stays Safe at Home
Most safety issues with milk happen after you bring it home. Proper storage is straightforward but important: keep your refrigerator between 38°F and 40°F (3°C to 4°C), and don’t leave milk sitting on the counter. At the right temperature, unopened milk generally stays good for five to seven days past its printed date. Once opened, plan to use it within two to three days of that date.
The sell-by or best-by date on the carton is a quality guideline, not a hard safety cutoff. Your senses are reliable tools for the final call:
- Smell: Fresh milk has almost no scent. A sour or off smell means it’s done.
- Texture: Pour some into a clear glass. Lumps or curdling mean the milk has spoiled.
- Color: A yellowish or greenish tint is a warning sign, though spoiled milk can also still look white, so don’t rely on color alone.
- Taste: If it passes the other tests but you’re still unsure, a small sip will tell you. Sour flavor means toss it.
Drinking a small amount of mildly spoiled milk is unlikely to cause serious illness in most people, but heavily spoiled milk with an obvious sour taste and thick texture should always be discarded.
Lactose Intolerance and Digestibility
For the roughly 36% of Americans with some degree of lactose malabsorption, the safety question isn’t about pathogens. It’s about whether milk will cause bloating, gas, cramps, or diarrhea. The good news is that most people with lactose intolerance can handle more milk than they think. Research from the National Institutes of Health suggests that many lactose-intolerant individuals can drink about one cup of milk (containing roughly 12 grams of lactose) without symptoms or with only mild discomfort.
Drinking smaller amounts spread throughout the day, pairing milk with food, or choosing lactose-free milk (which has the same nutrients with the lactose pre-broken down) are all practical ways to keep milk in your diet if you enjoy it. Fermented dairy like yogurt and aged cheeses contain less lactose naturally and are often tolerated even better.