Can Soured Milk Go Bad?

We're talking about milk that has a sour taste but hasn't curdled yet and is safe to consume. Typically, milk goes sour about three days after the expiration date. If unopened, it can last up to two weeks past the expiration date.

Can old sour milk make you sick?

Note: As long as it's pasteurized, sour milk is unlikely to make you sick, Gunders writes, because as milk ages, it becomes more acidic, creating an environment "unfriendly to microbes that might cause illness." Raw milk is a different story.]

Is it safe to drink milk that has gone sour?

You don't need to worry if you accidentally ingest a small sip of spoiled milk, but avoid drinking it in large — or even moderate — quantities. Drinking spoiled milk can cause digestive distress, such as vomiting, abdominal cramping, and diarrhea.