For most fevers in adults, acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) will bring your temperature down within an hour or two. Both are safe, effective, and available over the counter. Which one you choose depends on your situation, but ibuprofen tends to be slightly more effective at getting a fever under control. Beyond medication, staying hydrated and resting are the two most important things you can do while your body fights off whatever is causing the fever.
How Fever Reducers Work
When you’re sick, your brain’s temperature control center gets a signal to turn up the heat. The messenger behind that signal is a compound called prostaglandin E2, which builds up in the brain and changes the firing rate of the neurons that regulate your body temperature. The result: your internal thermostat resets to a higher point, and you feel cold and shivery even though your body is warming up.
Both acetaminophen and ibuprofen work by blocking the enzyme that produces prostaglandin E2. With less of that compound reaching your brain, your thermostat dials back down to normal. The key difference is that ibuprofen also reduces inflammation throughout the body, while acetaminophen primarily works on the temperature and pain signals in the brain. That’s why ibuprofen can be a better choice when a fever comes alongside sore muscles, a sore throat, or swollen glands.
Acetaminophen: Dosage and Limits
Adults and teenagers can take 650 to 1,000 milligrams of acetaminophen every four to six hours as needed. The absolute ceiling is 4,000 milligrams in 24 hours, though some products (like Tylenol Extra Strength) recommend staying at or below 3,000 milligrams per day. Going over these limits raises the risk of serious liver damage, which is the biggest safety concern with this drug.
The liver risk also means you need to watch for hidden acetaminophen in other products. Many cold and flu remedies, sleep aids, and combination pain relievers contain it. If you’re taking any of those alongside standalone acetaminophen, you can accidentally exceed the daily limit without realizing it. Check labels carefully, and avoid alcohol while using it.
Ibuprofen: Dosage and Limits
For fever or mild to moderate pain, adults can take 400 milligrams of ibuprofen every four to six hours as needed. Over-the-counter use should generally stay at or below 1,200 milligrams per day unless a doctor directs otherwise. Ibuprofen is harder on the stomach than acetaminophen, so taking it with food helps. It can also affect kidney function, making it a poor choice if you’re dehydrated, which is common during a fever with vomiting or diarrhea.
Naproxen as a Third Option
Naproxen sodium (Aleve) is another over-the-counter option for adults and children 12 and older. Its advantage is that it lasts longer, so you take it less often: one tablet every 8 to 12 hours, with a maximum of three tablets in 24 hours. For the first dose, you can take two tablets within the first hour. Like ibuprofen, naproxen is an anti-inflammatory, so it carries the same stomach and kidney considerations. If your fever hasn’t improved after three days of naproxen, it’s time to call a doctor.
Alternating Two Medications
If a single medication isn’t bringing your fever down enough, alternating acetaminophen and ibuprofen is a well-studied strategy. The typical approach is to take acetaminophen first, then follow with ibuprofen two to four hours later. A 2024 meta-analysis in the journal Pediatrics found that this alternating approach was roughly 3.5 times more likely to produce a normal temperature by four hours compared to acetaminophen alone. Combined or alternating therapy also performed significantly better at the six-hour mark.
Safety-wise, the same analysis found no difference in side effects between alternating therapy and using either drug alone, as long as both are taken at appropriate doses. The risk comes from losing track of what you took and when. If you go this route, write down each dose and the time, so you don’t accidentally double up on one medication.
Aspirin: Not for Children or Teens
Aspirin reduces fever through a similar mechanism, but it carries a unique and serious risk for anyone under 18. Children or teenagers who take aspirin during a viral illness like the flu or chickenpox face a small but real chance of developing Reye’s syndrome, a rare condition that causes dangerous swelling in the liver and brain. The risk is even higher in children with certain metabolic conditions, particularly fatty acid oxidation disorders. For this reason, aspirin should not be given to children or teenagers for fever, full stop.
Non-Drug Cooling Methods
Lukewarm sponge baths and cool compresses can bring a fever down faster than medication in the first 30 minutes to an hour. The catch is that they often cause shivering, which is uncomfortable, especially for children. Studies comparing tepid sponging to oral fever reducers show that by the two- to three-hour mark, the results are about the same. That makes sponging useful as a bridge while you wait for medication to kick in, but not a great standalone strategy.
Never use cold water, ice baths, or rubbing alcohol to cool a fever. These cause rapid cooling that triggers intense shivering, which can actually raise your core temperature. A lukewarm washcloth on the forehead or a brief lukewarm bath is enough.
Staying Hydrated
Fever increases how much fluid your body loses through sweat and faster breathing. Replacing those fluids is just as important as lowering the temperature itself. Water is fine for most people, but drinks with electrolytes (or oral rehydration solutions) are better when the fever comes with vomiting or diarrhea. If nausea makes it hard to drink, take small sips of about 30 milliliters (roughly two tablespoons) every three to five minutes rather than trying to gulp down a full glass.
General hydration targets are around 15 cups of fluid per day for men and 11 cups for women under normal conditions. During a fever, aim for at least that much, and more if you’re sweating heavily or losing fluids to diarrhea.
Fever Medications for Children
Children’s doses of acetaminophen and ibuprofen are based on weight, not age. The therapeutic ranges are 10 to 15 milligrams per kilogram of body weight for acetaminophen and 5 to 10 milligrams per kilogram for ibuprofen. Children’s formulations come in specific concentrations, so always use the measuring device included with the product rather than a kitchen spoon. Ibuprofen should be avoided in children who are dehydrated or at risk of dehydration, and in those with chickenpox, because of increased risks of kidney injury and severe skin infections.
Temperature Thresholds That Matter
A fever is generally defined as a temperature at or above 100.4°F (38°C) taken orally, rectally, or with an ear or forehead thermometer. An armpit reading of 99°F (37.2°C) or higher counts as well, though armpit readings tend to run lower than actual core temperature.
For babies under three months old, any fever of 100.4°F or higher needs immediate medical attention, regardless of how the baby seems otherwise. For older children, look for signs of dehydration (no wet diapers for 8 to 10 hours, crying without tears, dry mouth), stiff neck, repeated vomiting, confusion, belly pain, or a rash. A fever that persists beyond five days in a child also warrants a call to the doctor. For adults, the red flags are trouble breathing, chest pain, severe headache, stiff neck, or a fever that medication can’t bring down.