I left out cephalexin liquid for a week before using will it still work or is it bad to give 3 month old?

Please check with your Pediatrician. The medication should be stored and used as prescribed. Monitor your child's temperature and if the antibiotic is indicated, please request a new bottle from the pharmacy. Watch for rash, fever and poor feeding.

Suspension antibiotic like that one are generally potent for 1 week at room temperature and 2 wks in the refrigerator. I would rarely if ever give that med to a 3 mo old without a clear reason why, as others are likely preferred. I would not consider this med potent/worth using in the situation described.

Agree and add 2 points . By now the indication for your Dr’s prescription has likely changed. As a general rule, the conditions a med is kept in effect it more than time. Ex: leaving an Rx in a parked car , while in a store can expose a new med to scalding temperatures. Think of meds as bringing home frozen food. Temp matters .