Ibuprofen (Advil) is slightly more effective than acetaminophen (Tylenol) at reducing fever, particularly at the four-hour mark after taking a dose. A meta-analysis of nine fever trials involving over 1,000 children found that ibuprofen consistently lowered temperature more than acetaminophen at two, four, and six hours after treatment. That said, both medications work well, and the better choice often depends on your health profile rather than raw effectiveness alone.
How Each Drug Lowers a Fever
Both ibuprofen and acetaminophen reduce fever by lowering levels of a chemical messenger called PGE2 in the brain’s temperature-control center. When you’re sick, your body ramps up PGE2 production, which essentially resets your internal thermostat higher. Both drugs block the enzyme responsible for making PGE2, bringing your set point back down.
The key difference is scope. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID), so it also reduces inflammation throughout the body. Acetaminophen works primarily in the brain and has little anti-inflammatory effect. This makes ibuprofen a better fit when fever accompanies significant inflammation, like an ear infection or sore throat, but it also means ibuprofen carries side effects that acetaminophen does not.
How They Compare for Fever Reduction
In head-to-head studies, ibuprofen has a consistent edge. A large meta-analysis published in The Journal of Pediatrics found that at the standard dose of 10 mg/kg, ibuprofen produced meaningfully greater temperature drops than acetaminophen at every time point measured. The advantage was modest at two hours but roughly doubled by four hours.
A 2024 network meta-analysis from the American Academy of Pediatrics confirmed these findings. At four hours, high-dose ibuprofen was significantly more likely to bring a child to a fever-free state compared with acetaminophen alone. By six hours, however, that gap narrowed and the two drugs performed more similarly. In practical terms, ibuprofen tends to bring fever down a bit more and hold it down a bit longer during the middle hours of a dose, but neither drug is dramatically superior.
Onset and Duration of Action
Both medications start working within roughly 30 to 60 minutes when taken by mouth and last about four to six hours per dose. Acetaminophen tends to kick in slightly faster (around 30 to 45 minutes) compared to ibuprofen (closer to 30 to 60 minutes), though the difference is small and varies depending on whether you’re taking a liquid or a tablet. Liquid forms absorb faster for both drugs.
Standard dosing intervals differ. Acetaminophen can be taken every four to six hours, while ibuprofen is typically spaced every six to eight hours. This means acetaminophen gives you more flexibility to re-dose sooner if a fever climbs back up, even though each individual dose may not reduce the fever quite as much.
When Tylenol Is the Safer Choice
Acetaminophen is gentler on the stomach and kidneys. If you have a history of stomach ulcers, acid reflux, or kidney problems, it’s the better option. People taking blood thinners should also stick with acetaminophen, since ibuprofen can interfere with clotting and increase bleeding risk. For the same reason, acetaminophen is preferred during pregnancy (especially in the third trimester, when ibuprofen is contraindicated) and for infants younger than six months, who should not receive ibuprofen at all.
Acetaminophen’s main risk is liver damage, but this is almost exclusively a problem with overdose. The maximum safe amount is 4,000 milligrams in 24 hours for healthy adults. People with chronic liver disease should stay under 2,000 milligrams per day. The most common way people accidentally exceed the limit is by taking multiple products that all contain acetaminophen without realizing it, since the ingredient appears in hundreds of cold, flu, and sleep medications. Interestingly, the Mayo Clinic notes that acetaminophen at correct doses is generally considered safer than NSAIDs even for people with liver disease.
When Advil Is the Better Pick
Ibuprofen makes more sense when fever comes with inflammation or body aches, since it tackles both at once. It’s also a reasonable first choice for otherwise healthy adults and children over six months who don’t have stomach or kidney concerns.
Avoid ibuprofen if you have kidney disease, a history of GI bleeding, or are taking medications that affect kidney function or blood clotting. Drinking alcohol while using ibuprofen increases the risk of both stomach bleeding and liver damage.
Alternating Both Medications
For stubborn fevers, some doctors recommend alternating ibuprofen and acetaminophen. The AAP’s 2024 meta-analysis found that alternating the two drugs was significantly more effective than using acetaminophen alone. At four hours, alternating therapy brought roughly one in four additional children to a fever-free state compared to acetaminophen monotherapy. Combined therapy (taking both at the same time) was even more effective, with a number needed to treat of just three, meaning for every three children given the combination, one additional child became fever-free who wouldn’t have on acetaminophen alone.
The tradeoff is complexity. Because the two drugs have different dosing intervals (every four to six hours for acetaminophen, every six to eight for ibuprofen), alternating regimens are easier to mess up. The AAP recommends starting with one medication alone and only adding the second if the fever persists and the person remains uncomfortable. If you do alternate, writing down each dose and its timing helps prevent accidental double-dosing. The AAP also emphasizes that the goal of treating fever is comfort and hydration, not hitting a specific number on the thermometer.
No significant differences in side effects were found between single-drug and combination approaches in the studies reviewed, which is reassuring for short-term use.
Choosing Based on Your Situation
- Healthy adults with fever and body aches: Ibuprofen is slightly more effective and addresses inflammation.
- Stomach problems, kidney disease, or blood thinners: Acetaminophen is safer.
- Liver disease: Acetaminophen at reduced doses (under 2,000 mg/day) is still generally preferred over ibuprofen, despite what many people assume.
- Infants under 6 months: Acetaminophen only.
- Children over 6 months: Either drug works. Ibuprofen has a slight edge for fever reduction.
- Persistent fever with discomfort: Alternating or combining both drugs is more effective than either alone.
For most healthy people, the difference between the two is modest enough that either will do the job. Ibuprofen wins on raw fever-lowering power, acetaminophen wins on safety margin for sensitive groups, and using both strategically gives you the strongest effect when a fever won’t quit.