my doc told me to go by weight @mommy_faith even when he was small at 3 months before the actual shots

I did after my daughters two months shots and I didn't bother her it helped I'm not sure how much I followed the instructions on the bottle if your unsure call the doctor

@rachel8792, what if my son is 22 pounds but only 6 months? Lol he's a chunk. Do I go by the weight or age?

not after shots, it can hide any reactions baby may have.

The doctor recommended infant Tylenol after my sons two month shots. so I'm sure it's safe for a three month old.

It should say on the box or call your doctor or nurses on call line make sure it's the baby Tylenol