Infant medication dosing: how to dose safely and avoid mistakes

Giving medicine to a baby feels scary. Dosing errors are common, but a few clear rules make it easy and safe. This page gives quick, practical steps you can use right now: how to calculate doses, what medicines are OK by age, and when to call your pediatrician.

First rule: weigh your child, not guess. Medicines for infants are dosed by weight (mg per kg). Find the baby’s recent weight in kilograms or convert pounds to kg (divide pounds by 2.2). Always use the child’s current weight from a scale or clinic record.

How to calculate the dose

Decide the right mg/kg dose from trusted guidance, then multiply by the baby’s weight. Example: acetaminophen is commonly 10–15 mg/kg per dose. If your baby weighs 8 kg and you choose 15 mg/kg, that’s 120 mg per dose. Check your liquid medicine’s concentration (for example, many pediatric acetaminophen bottles are 160 mg/5 mL). To convert to mL: dose (mg) ÷ concentration (mg per mL) = mL to give. In the example: 120 mg ÷ (160 mg / 5 mL = 32 mg/mL) = about 3.75 mL. Use a syringe and round sensibly.

Example math again for ibuprofen: typical dose is 5–10 mg/kg every 6–8 hours for babies 6 months and older. For a 10 kg baby at 7.5 mg/kg, give 75 mg. If the bottle is 100 mg/5 mL, that’s 3.75 mL. Always check the label for the exact concentration before converting.

Practical safety tips

Use an oral syringe or dosing cup with clear markings. Never use kitchen teaspoons. Write the time and dose down so you don’t double up. Don’t give ibuprofen to babies under 6 months unless the doctor says so. For infants under 3 months with a fever of 100.4°F (38°C) or any concerning signs (refusing feeds, very sleepy, breathing fast), call the doctor right away.

Avoid aspirin in children (risk of Reye syndrome). Watch out for multiple products with the same active ingredient—many cold remedies contain acetaminophen. Don’t mix doses without checking if two medicines both contain the same drug. Store meds out of reach, at recommended temperatures, and toss expired medicine.

If math feels hard, ask a pharmacist to calculate the exact mL for you. When in doubt, contact your pediatrician. Having a clear plan—weight, mg/kg, concentration, syringe, and a record—keeps medicine time calm and safe. Keep questions? Reach out to your clinician or pharmacist before giving the first dose.