How much Tylenol or Motrin can I safely give my child?

Dr. Gwenn:

I have an 11month old son who weighs 20lbs. How much Tylenol or Motrin can I give him?


AC, Massachusetts


Dear AC:

Great question.  Figuring out over the counter medications dosing can be confusing, especially since kid’s weights are constantly changing and dosing is based on weight. You’ll notice that dosing guidelines on the medication packaging include ranges by weight and age.  These are ok in a pinch but are not very accurate because they cover a wide range of weights and are not precise for your child.

In addition to talking to your health care provider or pharmacist, you can do a simple calculation yourself to determine your child’s more accurate dose by just knowing your child’s weight, in either pounds or kilograms.

Here are the formulas we use for both Tylenol(acemaminophen) and Motrin/Advil(ibuprofen):

Tylenol: 15mg/kg/dose or 7mg/pound/dose every 4 hours.

Dose = 15xweight(kg) or 7xweight(lb)

Motrin: 10mg/kg/dose or 4.5mg/pound/dose every 6hours.

Dose = 10xweighg(kg) or 4.5xweight(lb)

So, based on your son’s current weight of 20lbs,  here’s how’d you’d figure out his current dose:

Tylenol:   20 x 7 = 140mg of tylenol. Tylenol comes in 80mg droppers or 160mg teaspoon. So, to not over dose him, you’d give him the closest reasonable dose which is about 120mg or 1 1/2 droppers of infant Tylenol or 3/4 Teaspoon of Children’s Tylenol.  When in doubt, go a bit less than a bit more if you are between doses.

Motrin: 20 x 4.5 – 90mg. Motrin comes 50 mg in the Infant dropper or 100 mg per teaspoon in the Children’s elixir. So, just shy of 1 teaspoon or just about 2 droppers of the 50mg line would be your son’s dose of Motrin.

When children are infants and toddlers, their weights change rapidly so you’ll want to be sure you have an idea of your child’s current weight every month or so until your child is age 3.  After that, the weight gain slows down and you can get a weight every 6 months without much concern.

In a pinch, you can figure out your infant’s weight on any home scale by weighing yourself holding your infant and subtracting your weight. Home scales are very inaccurate for very teeny weights, such as 20ish pounds and less.

Finally, be sure you really need to give either medication before you give it. Your pediatrician can guide you best on that front if you are all uncertain.

Dr. Gwenn

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