Doctors give trusted answers on uses, effects, side-effects, and cautions: Dr. Ferguson on infant tylenol dosage for 3 month old: Usually the parents have more discomfort than baby. Fewer drugs are better than more drugs. Cold teething rings are safe to use without relying on Tylenol (acetaminophen) 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. 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. I have a 3 month old daughter. She's been coughing for about a week and a half, but she has no other symptoms other than stuffy nose. I brought her to a nurse but she just told me to but salted water up her nose to get the boogies out. She weights almost 15 pounds and has a slight fever of 100.5. She has been very cranky, but I think its just a cold, as everybody in my family has had it, and her doctor said that she will probably get it to! My son will be 3 mo old in 3 days.He's already started breaking his first tooth. At night the pain seems to be too overwhelming for him. I give him day-time formula baby oragel during the day and the night-time formula at night. 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. Fewer drugs are better than more drugs. Cold teething rings are safe to use without relying on Tylenol (acetaminophen) I would do.4 to be safe, and then wait it out about an hour and if she isn't feeling better do half of that dose (where a.2 would be if they had one) up to a.4 depending on her symptoms.