Question

How long can you keep an onion after it has been cut?

Answer 1

If you plan to keep onions for longer than a day after cutting them you should place the cut onion or cut onions into a sealed container and then refrigerate the onions in the container.

When the onions are in a sealed container in the refrigerator the cut onions should last up to 7 days before going bad.

Answer 2

Onions can last up to 7 days after being cut as long as you refrigerate them.

If you cut the onion and leave it out overnight then the onion should be thrown out because it could cause food poisoning due to bacteria that the onion attracts when not being refrigerated.