For most adults with a fever, acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) are the two best options. Both work well at bringing a fever down, and at standard doses they perform similarly. The choice between them usually comes down to your health history and what you already have in your medicine cabinet.
Acetaminophen vs. Ibuprofen
These two medications lower fever through different pathways in the body, but the end result is comparable. A review from Penn State looked at head-to-head comparisons and found no significant difference in fever reduction over 6, 12, 24, or 48 hours when both are taken at full recommended doses. At the lower end of over-the-counter dosing, ibuprofen may have a slight edge, but it’s a modest difference.
Acetaminophen is generally the gentler option. It’s processed by the liver rather than affecting the stomach lining, so it’s easier on your gut. The FDA sets the maximum at 4,000 mg per day for adults and children 12 and older, but many doctors suggest staying under 3,000 mg per day to be safe, especially if you drink alcohol regularly or have any liver concerns. You can take it every 4 to 6 hours.
Ibuprofen belongs to the NSAID family (along with naproxen). It reduces both fever and inflammation, which can be helpful if your fever comes with body aches or a sore throat. You can take it every 6 to 8 hours. However, NSAIDs carry real risks for certain people. If you have kidney disease, a history of stomach ulcers, or heart failure, ibuprofen is not a good choice. People over 65 are also at higher risk for kidney problems from NSAIDs, especially if they’re dehydrated from the fever itself.
One particularly dangerous combination: if you take a blood pressure medication (an ACE inhibitor or ARB) along with a diuretic, adding an NSAID like ibuprofen creates what pharmacologists call a “triple whammy” for your kidneys. That combination raises the rate of acute kidney injury, with the highest risk in the first 30 days. If you take blood pressure medication, stick with acetaminophen for fever.
What to Take During Pregnancy
Acetaminophen is the only widely recommended fever reducer during pregnancy. The American College of Obstetricians and Gynecologists has affirmed its safety, noting that untreated fever during pregnancy can itself cause harm. NSAIDs like ibuprofen are generally avoided, particularly in the third trimester, when they can affect fetal development.
What to Give Children
Children can take acetaminophen or ibuprofen, but dosing is based on weight, not age. Both medications come in liquid suspensions and chewable tablets calibrated for smaller bodies.
A few critical rules for kids:
- Under 3 months: Do not give any fever medication without a doctor’s guidance. Any fever in a baby this young needs immediate medical attention.
- Under 6 months: Only acetaminophen is appropriate. Ibuprofen is not recommended before 6 months.
- Acetaminophen: Can be given every 4 to 6 hours, up to 5 doses in 24 hours.
- Ibuprofen: Can be given every 6 to 8 hours, up to 4 doses per day.
Never give aspirin to children or teenagers. Aspirin use during viral illnesses like the flu or chickenpox is linked to Reye’s syndrome, a rare but serious condition that causes swelling in the liver and brain. This applies to plain aspirin and any product that contains it. The only exception is children with specific chronic conditions, like Kawasaki disease, who take aspirin under close medical supervision.
Some studies suggest alternating acetaminophen and ibuprofen may bring a fever down slightly better than either one alone. However, the results are mixed, and the bigger risk is accidentally double-dosing or losing track of which medication was given last. If you do alternate, write down each dose and the time.
Why Fluids Matter as Much as Medication
A fever increases the amount of water your body loses through the skin. For every degree Celsius above 38°C (100.4°F), your body’s fluid loss through the skin increases by roughly 10%. A fever of 39.5°C (103°F), for example, means you’re losing about 15% more fluid than normal just sitting still. This is on top of any fluid lost from sweating, vomiting, or diarrhea that often accompany illness.
Water is fine for most adults. If you’ve been sick for more than a day, or if you’re vomiting or have diarrhea, an oral rehydration solution or a drink with electrolytes helps replace the sodium and potassium you’re losing. For children, pedialyte-style rehydration drinks are more effective than water alone. Signs that dehydration is becoming a problem include dark urine, dizziness when standing, dry mouth, and in children, fewer wet diapers or no tears when crying.
When a Fever Needs More Than Home Treatment
Most fevers are the body’s normal response to infection and resolve within a few days. But certain thresholds and symptoms signal something more serious.
For adults, a temperature of 103°F (39.4°C) or higher usually means you’ll feel significantly ill. Seek medical care if a fever at any level comes with trouble breathing, chest pain, a severe headache, a stiff neck, a rash, or joint swelling. A fever lasting more than five days also warrants evaluation, even if it’s not extremely high.
For children, the number on the thermometer matters less than how the child looks and acts. A child who remains playful with a fever of 102°F may need nothing more than fluids and rest. A child who is unusually fussy, lethargic, or not improving after taking fever-reducing medication needs medical attention regardless of the exact temperature. Any signs of dehydration in a child with a fever should also prompt a call to your pediatrician.