14month old son.how much tylenol (acetaminophen) to give when fever?current temp is 99.8

Depends on weight: The dose of Tylenol (acetaminophen) is based on weight, and the box or bottle should have a chart listing the dosage for different weight ranges. However, if his temp is only 99.8, look at how he's feeling. If he's happy, there's really no need to give anything, especially since fever helps our bodies fight off infection. If he's cranky or in pain, then certainly give it.

What weight?: To give the most precise dose you need to do it based on weight. Typically for tylenol (acetaminophen) you want to give 10-15 mg/kg per dose every 4-6 hrs as needed. However, I don't think your child needs tylenol (acetaminophen) for a temp of 99.8. Of course if your child looks uncomfortable you can try a dose.