Fed 5 month old 6 ounces of concentrated baby formula but forgot to add water. What will happen to baby

Fed 5 month old baby 6 ounces of concentrated formula without adding water will she be OK

It happens, and being a one off, baby will likely be fine. See how she acts, and what her next bowel movement or two are like. Whenever in doubt, always best to call her doctor. Even at night, they should have someone on call or be able to get back to you.

She will be okay, you might want to dilute the next couple feeds a little bit to make sure she's hydrated.

It happens, I can tell stories about fun times formula feeding.

She might be a bit constipated, but she'll be fine. Give her some water in a bottle, that will help if she does get a bit stopped up. But other than that, she'll be just fine. :)