The two most effective over-the-counter options for bringing down a fever are acetaminophen (Tylenol) and ibuprofen (Advil, Motrin). Both work well, both are safe for most adults at recommended doses, and both start lowering your temperature within about 30 to 60 minutes. Choosing between them comes down to your health history, your age, and how long you need relief to last.
How Fever Reducers Work
When your body fights an infection, it produces a chemical called prostaglandin E2 in the brain. This chemical essentially turns up your internal thermostat, raising your body temperature to create a less hospitable environment for viruses and bacteria. Fever reducers block the enzyme responsible for making that chemical, which brings the thermostat back down. Both acetaminophen and ibuprofen use this same basic mechanism, though they differ in other ways. Ibuprofen also reduces inflammation throughout the body, while acetaminophen does not.
Your Main Options
Acetaminophen (Tylenol)
Acetaminophen is a pure pain and fever reducer without anti-inflammatory effects. It kicks in within 30 to 45 minutes and lasts about 4 to 6 hours. Adults can take up to 4,000 milligrams in a 24-hour period, though staying under that ceiling is important. Acetaminophen overdose is the most common cause of acute liver failure, and it’s easier to exceed the limit than you’d think because many cold, flu, and allergy medications already contain acetaminophen. Always check the active ingredients on any other medicines you’re taking.
For people with liver disease, the safe limit drops to under 2,000 milligrams per day in divided doses. If your liver is healthy and you stick to the label, acetaminophen is one of the gentlest options available.
Ibuprofen (Advil, Motrin)
Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that reduces fever, pain, and inflammation. It takes 30 to 60 minutes to start working and lasts 4 to 6 hours. Because it’s an NSAID, it can irritate the stomach lining and affect kidney function, especially with long-term use or dehydration. People with kidney problems, stomach ulcers, or a history of gastrointestinal bleeding should be cautious. NSAIDs can also damage the liver, particularly when combined with alcohol.
Naproxen (Aleve)
Naproxen is another NSAID that works similarly to ibuprofen but lasts longer, up to 7 hours per dose. That longer duration means fewer doses throughout the day, which some people prefer. The same stomach, kidney, and liver cautions that apply to ibuprofen apply here too.
Aspirin
Aspirin reduces fever effectively, but it carries one critical restriction: never give aspirin to children or teenagers. It has been linked to Reye’s syndrome, a rare but serious condition that causes swelling in the liver and brain during viral illnesses like the flu or chickenpox. For adults without bleeding disorders or stomach issues, aspirin remains a viable option, but ibuprofen and acetaminophen are generally preferred.
Fever Medicine for Children
For kids, acetaminophen and ibuprofen are the two safe choices. Aspirin is off the table entirely. Children’s doses are based on weight, not age, so weigh your child first and use the dosing chart on the package. If you don’t know the weight, age is a backup guide, but weight is more accurate.
Children’s liquid acetaminophen comes in a standardized concentration of 160 milligrams per 5 milliliters. For children under 12, doses can be given every 4 hours, with a maximum of 5 doses in 24 hours. Extra-strength tablets (500 mg) should not be given to children under 12, and extended-release formulations (650 mg) are not appropriate for anyone under 18.
Babies younger than 3 months with any fever need immediate medical attention, regardless of how high the temperature is. Their immune systems are too immature for a wait-and-see approach.
Alternating Acetaminophen and Ibuprofen
If a single medication isn’t controlling your child’s fever well enough, alternating between acetaminophen and ibuprofen is a strategy many parents use. A 2024 meta-analysis published by the American Academy of Pediatrics found that alternating or combining these two medications was more effective at keeping children fever-free than using either one alone, with no increase in side effects.
The typical approach is to give acetaminophen first, then follow with ibuprofen 2 to 4 hours later, continuing to alternate on their individual schedules. This works because the two drugs lower fever through slightly different pathways and peak at different times. The key risk is losing track of what you gave when, so write down each dose and the time. This strategy is also reasonable for adults, though it’s studied more extensively in children.
Picking the Right One for You
If you have a healthy liver and kidneys and no other medications in the mix, either acetaminophen or ibuprofen will work. A few situations tip the balance one way:
- Stomach problems or ulcers: Choose acetaminophen. NSAIDs like ibuprofen irritate the stomach lining.
- Liver disease: Acetaminophen is still generally safer than NSAIDs at low doses (under 2 grams per day), but confirm with your doctor.
- Kidney problems: Avoid ibuprofen and naproxen. Acetaminophen is the safer choice.
- Inflammation along with fever: Ibuprofen or naproxen will address both, while acetaminophen only targets the fever and pain.
- Already taking cold or flu medicine: Check the label. Many combination products contain acetaminophen, and doubling up can push you past the daily limit without realizing it.
When a Fever Needs More Than Medicine
Most fevers in adults are the body doing its job and don’t need aggressive treatment. If you’re mildly uncomfortable at 100 or 101°F, you can simply rest, drink fluids, and skip the medication entirely. Fever reducers treat the symptom, not the underlying illness.
Adults with temperatures of 103°F (39.4°C) or higher typically look and feel noticeably sick and benefit from medication to bring the temperature down. A fever that persists beyond three days, keeps climbing despite medication, or comes with confusion, stiff neck, severe headache, or difficulty breathing warrants a call to your doctor or a trip to urgent care. For infants under 3 months, any fever at all is reason to seek help immediately.