(Acetaminophen is also known as paracetamol and sold under brand names such as Tylenol, Tempra, FeverAll, Mapap, Ofirmev, etc.) Acetaminophen/Tylenol safety tips The correct dose for your child is based on weight , not age. Cold teething rings are safe to use without relying on Tylenol (acetaminophen) Doctors give trusted answers on uses, effects, side-effects, and cautions: Dr. Ferguson on 3 month old tylenol dosage: Usually the parents have more discomfort than baby. Old infant drops: 80 mg/0.8 ml per dropper (shake well before using) New infant liquid: 160 mg/5 ml per included syringe (shake well before using) Children's liquid: 160 mg/5 ml per teaspoon (shake well before using) My doctor said that I can give my 2 month old baby tylenol after the vaccines as she may develop a fever and may get cranky. I forgot to ask the doctor for the dosage. Infant Tylenol Dosage Chart by Weight You’ll notice on the bottle of Infant Tylenol that it doesn't give dosages for children under 2 years old, but instead says to call your doctor. She'll be able to recommend whether or not to give Tylenol and what the correct dosage should be based on baby's weight. When to Give Tylenol. Tylenol, also known as acetaminophen, can reduce your little one’s fever and ease any discomfort. At 2 months, though, if your baby runs a fever over 100.4 degrees or seems to be in much discomfort, you should talk to your pediatrician. If your child is under 2 years of age, be sure to ask your doctor for the right dose. Under 2 Years. If your child is under 2 years of age, be sure to ask your doctor for the right dose. My daughter is 20 months old, but she is 24 lbs. But even before, when she was just a little under that weight, we were using children's stuff, as the infant no longer did much for her.