Fever Medication for Kids: Acetaminophen vs. Ibuprofen Safety Guide

What to Know Before Giving Fever Medicine to Your Child

Fevers in kids are scary. Your baby feels hot, is fussy, won’t eat, and you just want to make them better. It’s natural to reach for medicine-but which one? Acetaminophen or ibuprofen? And how much? Getting this wrong can lead to real harm. The good news? Both are safe when used correctly. The bad news? Many parents get it wrong-by dosing by age instead of weight, mixing brands, or using adult medicine by accident.

How Acetaminophen and Ibuprofen Work Differently

Acetaminophen (also called paracetamol) and ibuprofen both reduce fever and ease pain, but they work in different ways. Acetaminophen mainly targets the brain’s fever center. Ibuprofen also does that, but it goes further-it reduces inflammation. That’s why ibuprofen often works better for ear infections, sore throats, or teething pain where swelling is part of the problem.

Pharmacologically, acetaminophen kicks in faster-about 30 to 60 minutes after giving it. Ibuprofen takes a bit longer, usually 1 to 2 hours, but it lasts longer too. One dose of ibuprofen can keep a fever down for up to 8 hours. Acetaminophen? More like 4 to 6 hours. That means fewer doses with ibuprofen, which is why many parents report it works better for overnight fevers.

Dosing: Weight Matters, Not Age

Never give fever medicine based on age alone. That’s the most common mistake. A 15-pound baby needs a completely different dose than a 25-pound toddler-even if they’re both 12 months old. The right dose is always based on weight in kilograms (kg).

For acetaminophen: 7-15 mg per kg of body weight, every 4-6 hours. Maximum daily dose: 75 mg/kg. For ibuprofen: 4-10 mg per kg, every 6-8 hours. Maximum daily dose: 40 mg/kg. Always check the label. Liquid formulations have changed. Since 2011, infant acetaminophen is standardized to 160 mg per 5 mL. Older bottles (80 mg per 0.8 mL) are outdated and dangerous if used by mistake.

Example: A 10 kg (22 lb) child. Acetaminophen dose: 70-150 mg per dose. Ibuprofen dose: 40-100 mg per dose. Use the syringe or cup that comes with the medicine. Never use a kitchen spoon. A teaspoon holds 5 mL, but not all teaspoons are the same. The dosing tool is designed for precision.

Safety: What the Research Really Says

For years, doctors told parents acetaminophen was safer for babies under 3 months. That’s no longer the full picture. A 2021 meta-analysis of 85 studies, published in American Family Physician, found ibuprofen is just as safe as acetaminophen in children under two-when dosed correctly. There’s no higher risk of kidney injury or liver damage if you stick to the weight-based dose.

But here’s the catch: both medicines can be dangerous if you give too much. Acetaminophen overdose is the leading cause of acute liver failure in children in the U.S. Ibuprofen overdose can cause stomach bleeding or kidney stress. Neither should be given for more than 72 hours straight without seeing a doctor.

Also, avoid combination products. Many cold and flu syrups contain acetaminophen already. Giving extra acetaminophen on top of that? That’s how accidental overdoses happen. Read every label. If you’re unsure, don’t give it.

Which One Works Better for Fever?

Studies show ibuprofen reduces fever more effectively than acetaminophen. In one analysis of five trials, children given ibuprofen were 1.86 times more likely to be fever-free at 4 hours. The absolute difference? About 12.5% more kids were afebrile. At 24 hours, that gap widened. Ibuprofen had an 18.5% higher chance of keeping the fever down.

Why? It’s not magic. It’s pharmacology. Ibuprofen’s longer half-life means it stays active in the body longer. Acetaminophen wears off faster, so the fever often comes back sooner. For high fevers (above 39°C or 102.2°F), ibuprofen often gives better, longer-lasting relief.

But for mild fevers or if your child has a sensitive stomach, acetaminophen might be easier to tolerate. Ibuprofen can cause mild nausea or upset stomach in about 1 in 5 kids. Acetaminophen rarely does.

Alternating Medications: Good Idea or Risk?

Many parents alternate acetaminophen and ibuprofen every 3 hours to keep the fever down. It sounds smart. But it’s risky. The American Academy of Pediatrics doesn’t recommend it unless a doctor says so. Why? Because it’s easy to lose track. You end up giving two doses too close together. You might accidentally overdose.

One 2022 study of 4,852 parents found 63% had alternated at least once. But in the same group, 31% said they’d given the wrong dose because they got confused. A 2023 Pediatrics study showed alternating didn’t improve outcomes over using one medicine correctly. If the fever isn’t breaking, call your pediatrician. Don’t guess with doses.

What About Babies Under 6 Months?

This is where things get tricky. The American Academy of Pediatrics advises against giving ibuprofen to babies under 6 months unless a doctor says it’s okay. Why? There’s less safety data in this age group. Their kidneys are still developing, and dehydration risk is higher.

For babies under 3 months with a fever of 38°C (100.4°F) or higher, you should go to the ER. Fever in newborns can be a sign of serious infection. Don’t wait to give medicine. Don’t try to treat it at home. Call your doctor or go to the hospital immediately.

For babies 3-6 months, acetaminophen is the first choice. But even then, check with your pediatrician first. Don’t assume it’s okay just because it’s “over the counter.”

Administration Tips That Save Lives

How you give the medicine matters as much as how much you give.

• Always use the syringe or cup that came with the bottle. Never use a kitchen spoon.
• Hold your child upright. Never give medicine while they’re lying flat. Choking risk goes up.
• Wait until the child swallows before giving more. Some kids spit out half of it.
• Never use adult medicine. Even a small amount of adult ibuprofen can be toxic to a baby.
• Store medicine out of reach. Most pediatric poisonings happen because kids get into the cabinet.

Also, check expiration dates. Liquid medicine degrades faster than pills. If it’s been sitting for over a year, throw it out.

What About Asthma Risk?

Some studies suggest early acetaminophen use might be linked to a higher chance of developing asthma later. A 2022 meta-analysis in the European Respiratory Journal found children exposed to acetaminophen in their first year had a 1.6 times higher risk. But this doesn’t mean you should avoid it when your child has a fever. It means you shouldn’t give it routinely for every little bump or sniffle.

Use medicine only when needed. If your child has asthma or a family history of it, talk to your doctor about whether ibuprofen might be a better option for fever control.

What’s the Bottom Line?

For kids over 6 months: ibuprofen is often more effective for fever and pain, lasts longer, and is just as safe as acetaminophen when dosed by weight.

For babies 3-6 months: acetaminophen is the standard first choice, but always check with your doctor first.

For babies under 3 months: don’t give any fever medicine without going to the hospital.

Always use the dosing tool. Always dose by weight. Never mix medicines unless your doctor says so. And if the fever doesn’t come down after 24 hours, or your child looks very sick-lethargic, not drinking, breathing fast, rash-call your doctor. Medicine helps, but it doesn’t fix the cause.

When to Call the Doctor

• Fever lasts more than 72 hours
• Child is under 3 months with any fever
• Child is not drinking, urinating less than 3 times a day
• Child is unusually sleepy, hard to wake, or unresponsive
• Child has a stiff neck, rash that doesn’t fade when pressed, or seizures
• You’re unsure if you gave the right dose

Common Myths About Fever Medicine

• Myth: Fever is dangerous and must be brought down immediately. Truth: Fever is a sign your child’s body is fighting infection. Lowering it doesn’t speed recovery-it just makes them more comfortable.
• Myth: Acetaminophen is always safer for babies. Truth: Both are safe when used correctly. Ibuprofen has better data for kids over 6 months.
• Myth: More medicine = faster relief. Truth: Overdose can cause liver failure or kidney damage. More is not better.
• Myth: I can use the same bottle for both kids. Truth: Each child needs their own dosing tool. Cross-contamination and wrong doses happen easily.