How to determine the right dose of medicine for your child when they have fever?
How much medicine should I give my child to reduce their fever? How much acetaminophen/paracetamol is enough? What about ibuprofen? How long should I wait before giving them a second dose? Can I combine or alternate between the two?
You will find the answers to all these questions and more in the post below.
Prior to reading this section I would like to emphasize that you may use this site as a guideline to help you calculate the correct dose of medicine for your child. But always remember to look at the box and label of the medicine you are giving them. The medicines mentioned below are available in North America. Different countries may offer different forms of these medications, so always remember to read the label!
Some more basic concepts regarding acetaminophen and ibuprofen that you should be familiar with…
As I have previously mentioned, fever-reducing medications for children include acetaminophen/paracetamol (also available as Tylenol), and ibuprofen (also available as Advil or Motrin).
The concepts are simple:
– Provided your child is older than 3 months and has no significant past medical history, both medications work equally well and are safe to use.
– The correct dose of acetaminophen (paracetamol, Tylenol) for a child is 15mg for every 1kg body weight. The maximum dose that can be given to a child is 500 mg. After giving them one dose, you must wait 5 hours before giving them another dose of paracetamol.
– The correct dose of ibuprofen (Advil or Motrin) is 10mg for every 1kg body weight. The maximum dose that can be given to a child is 400 mg. After giving them one dose, you must wait 8 hours before giving them another dose.
Please note that there are exceptional cases, when a larger dose of these two medications can be administered, but the doses mentioned above are the commonly acceptable and safe doses. In my opinion, using larger doses will lead to more harm than benefit.
Also, I am aware that other sources may advise different minimal time intervals between doses. Nonetheless, taking all benefits (optimal fever reduction) and potential harms (side effects, toxicity) into account, I truly believe that the waiting times I mention above ensure efficacy and safety for you and your child.
Paracetamol/acetaminophen
The correct dose of paracetamol/acetaminophen for a child is calculated as follows:
For every kg of body weight, the child will need 15mg of paracetamol.
If, for example, a 4 months old child weighs 5.5kg, they will need 82.5mg of paracetamol.
Next, with the help of the ratio-proportion method, we are able to calculate the volume of oral suspension that this translates into. If you know how to do this, that’s great! If not, just use the table below to find out how much Tylenol (oral suspension) your child needs depending on their weight. Also, if you did the calculation on your own, you can double check to make sure your calculation is correct by using the table.
How do I get 82.5mg of paracetamol?
As you probably know, paracetamol, or Children’s Tylenol, comes in several forms:
– Children’s Tylenol Oral Suspension containing 160mg in every 5mL of suspension
– Infant’s Tylenol Drops, containing 80mg in every 1mL
Two other forms that this child will not be able to take are:
– Children’s Tylenol Easy Dissolve Powder, containing 160mg in each individual pack
– Children’s Tylenol Chewables, containing 160mg in every tablet
These two forms come in pre-set doses that cannot be divided or cut and so we would be unable to get a dose of 82.5mg using these. Of-course, a 5.5-month-old infant would also be unable to chew a tablet.
After giving the child a dose of paracetamol, you need to wait 5 hours before it is safe to give another dose.
Paracetamol doses according to weight
| Weight (kg) | Required Dose (mg) | Dose for Children’s Tylenol Oral Suspension in ml (containing 160mg in every 5ml) | Doses for Infant’s Tylenol Drops, in ml (containing 80mg in every 1ml)
|
| 3 | 45 | 1.4 | 0.5 |
| 4 | 60 | 1.9 | 0.8 |
| 5 | 75 | 2.3 | 0.9 |
| 6 | 90 | 2.8 | 1.1 |
| 7 | 105 | 3.3 | 1.3 |
| 8 | 120 | 3.8 | 1.5 |
| 9 | 135 | 4.2 | 1.7 |
| 10 | 150 | 4.7 | 1.9 |
| 11 | 165 | 5.2 | 2.1 |
| 12 | 180 | 5.6 | 2.3 |
| 13 | 195 | 6.1 | 2.4 |
| 14 | 210 | 6.6 | 2.6 |
| 15 | 225 | 7.0 | 2.8 |
| 16 | 240 | 7.5 | 3.0 |
| 17 | 255 | 8.0 | 3.2 |
| 18 | 270 | 8.4 | 3.4 |
| 19 | 285 | 8.9 | 3.6 |
| 20 | 300 | 9.4 | 3.8 |
| 21 | 315 | 9.8 | 3.9 |
| 22 | 330 | 10.3 | 4.1 |
| 23 | 345 | 10.8 | 4.3 |
| 24 | 360 | 11.3 | 4.5 |
| 25 | 375 | 11.7 | 4.7 |
| 26 | 390 | 12.2 | 4.9 |
| 27 | 405 | 12.7 | 5.1 |
| 28 | 420 | 13.1 | 5.3 |
| 29 | 435 | 13.6 | 5.4 |
| 30 | 450 | 14.0 | 5.6 |
| 31 | 465 | 14.5 | 5.8 |
| 32 | 480 | 15.0 | 6.0 |
Ibuprofen
The correct dose of ibuprofen for a child is calculated as follows:
For every kg of body weight, the child will need 10mg of ibuprofen.
If, for example, a 7-month-old child weighs 7kg, and they have no significant past medical history, they will need 70mg of ibuprofen.
Next, with the help of the ratio-proportion method, we are able to calculate the volume of oral suspension that this translates into. If you know how to do this, that’s great! If not, just use the table below to find out how much Ibuprofen/Advil/Motrin (oral suspension) your child needs depending on their weight. Also, if you did the calculation on your own, you can double check to make sure your calculation is correct by using the table.
How do I get 70mg of ibuprofen?
As you probably know, ibuprofen, or Children’s Motrin or Advil, comes in several forms:
– Children’s Liquid Ibuprofen containing 100mg in every 5mL of suspension
– Infant’s Ibuprofen Drops, containing 50mg in every 1.25mL
Another available form that this child will not be able to take is:
– Children’s Ibuprofen Chewable Tablets, containing 50mg in each individual tablet
This form comes in pre-set doses that cannot be divided or cut and so we would be unable to get a dose of 70mg using this. Of-course, a 7-month-old infant would also be unable to chew a tablet.
After giving the child a dose of ibuprofen, you need to wait 8 hours before it is safe to give another dose.
Ibuprofen doses according to weight (for children aged 3 months and over)
| Weight (kg) | Required Dose (mg) | Dose for Liquid Ibuprofen Oral Suspension, in ml (containing 100mg in every 5ml) | Doses for Infant’s Ibuprofen Drops, in ml (containing 50mg in every 1.25ml) |
| 4 | 40 | 2.0 | 1.0 |
| 5 | 50 | 2.5 | 1.3 |
| 6 | 60 | 3.0 | 1.5 |
| 7 | 70 | 3.5 | 1.8 |
| 8 | 80 | 4.0 | 2.0 |
| 9 | 90 | 4.5 | 2.3 |
| 10 | 100 | 5.0 | 2.5 |
| 11 | 110 | 5.5 | 2.8 |
| 12 | 120 | 6.0 | 3.0 |
| 13 | 130 | 6.5 | 3.3 |
| 14 | 140 | 7.0 | 3.5 |
| 15 | 150 | 7.5 | 3.8 |
| 16 | 160 | 8.0 | 4.0 |
| 17 | 170 | 8.5 | 4.3 |
| 18 | 180 | 9.0 | 4.5 |
| 19 | 190 | 9.5 | 4.8 |
| 20 | 200 | 10.0 | 5.0 |
| 21 | 210 | 10.5 | 5.3 |
| 22 | 220 | 11.0 | 5.5 |
| 23 | 230 | 11.5 | 5.8 |
| 24 | 240 | 12.0 | 6.0 |
| 25 | 250 | 12.5 | 6.3 |
| 26 | 260 | 13.0 | 6.5 |
| 27 | 270 | 13.5 | 6.8 |
| 28 | 280 | 14.0 | 7.0 |
| 29 | 290 | 14.5 | 7.3 |
| 30 | 300 | 15.0 | 7.5 |
| 31 | 310 | 15.5 | 7.8 |
| 32 | 320 | 16.0 | 8.0 |
| 33 | 330 | 16.5 | 8.3 |
| 34 | 340 | 17.0 | 8.5 |
| 35 | 350 | 17.5 | 8.8 |
| 36 | 360 | 18.0 | 9.0 |
| 37 | 370 | 18.5 | 9.3 |
| 38 | 380 | 19.0 | 9.5 |
| 39 | 390 | 19.5 | 9.8 |
| 40 | 400 | 20.0 | 10.0 |
Paracetamol and Ibuprofen – how to give a combination of both
Okay my friends, so one of the things that my patients and their families find most surprising is the fact that there is no minimal time interval that you are advised to wait between a dose of paracetamol and a dose of ibuprofen. Hypothetically speaking, you could even give the two together. But obviously, this would make no sense.
I usually recommend the use of one only to reduce fever, as long as the fever is responding to it and the pain improves. However, if parents are interested in maximizing the potential ability of these medicines to reduce fever, they can combine or alternate the two medications, without any problem, as long as they maintain a minimum time interval of 5 hours between 2 paracetamol doses, and 8 hours between 2 ibuprofen doses.
I realize that some sources do not advise the combination of these two medicines. I think the idea behind this is to prevent overuse of these two drugs. However, if you follow this website to guide you with dosing and give the correct doses, there is no fear of overuse/overdose.
Furthermore, there is scientific evidence that combining the two drugs may be more efficient in reducing fever and symptoms than using only one of them alone, so why not?
Here are two examples of how you can combine paracetamol and ibuprofen
1. A 1.5-year-old child, who has no significant past medical history, weighs 12.5kg and has fever. He receives an adequate dose of paracetamol at 4:00pm. His fever drops for a few hours. However, at 7pm his fever spikes up again. What can we do now?
Since it has only been 3 hours since his prior dose of paracetamol, we are unable to give him another dose of paracetamol just yet. We can either wait 2 more hours, and then give him another dose of paracetamol (and in the meantime reduce his fever without the use of medications, using some of the methods discussed here), or we can give him ibuprofen now.
Remember, there is no minimal time you are required to wait between a dose of paracetamol and a dose of ibuprofen.
2. A 9-month-old child, who has no significant past medical history and weighs 8.5kg. It is now 7:00pm and he has fever. The mother would like to give him a dose of ibuprofen, because the last time he had fever the ibuprofen worked very well and the mother also prefers giving him a drug that will last for a longer period of time (ibuprofen normally works for 8 hours while paracetamol works for 5 hours).
The mother gives the child an adequate dose of ibuprofen. However, at midnight, she notices that the child has cold feet and hands, and his fever begins to rise again. It has only been 5 hours since his previous dose of ibuprofen, and she will need to wait 3 more hours before she can give the next dose of ibuprofen. In the meantime, she can give him a dose of paracetamol. The next dose of ibuprofen can still be given at 3:00 am (if he needs it).
The only important concept to remember is waiting for 5 hours between two doses of paracetamol and 8 hours between two doses of ibuprofen.
There is no problem in combining or alternating between the two groups of medications.
To conclude, this is a basic chapter and I believe all parents will benefit from reading and understanding the concept of fever reduction in children.
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