How to Take Your Baby's Temperature: Methods and Accuracy

Taking your baby's temperature accurately is essential for determining if your child has a fever and deciding whether medical care is needed. Different thermometer types and methods are available, each with varying accuracy levels and age-appropriateness. Learning the correct technique ensures reliable readings and helps you make informed health decisions.

Types of Thermometers

Digital Thermometers

Digital thermometers are the most commonly recommended and affordable option. They display temperature digitally and beep when the reading is complete. They work for rectal, oral, and underarm temperatures.

Pros: Fast (30-60 seconds), affordable, easy to read, versatile.

Cons: Less accurate if not inserted properly; reading may vary slightly between uses.

Forehead/Temporal Thermometers

These infrared thermometers scan the temporal artery on the forehead. They're non-invasive and fast, showing results in 1-3 seconds.

Pros: Quick, non-invasive, no discomfort, good for sleeping babies.

Cons: Less accurate than rectal readings, affected by sweating or room temperature, can vary significantly.

Ear Thermometers (Tympanic)

Infrared ear thermometers measure the temperature at the eardrum. They're quick but require proper insertion into the ear canal.

Pros: Fast (2-3 seconds), less invasive than rectal, good for older babies and toddlers.

Cons: Less accurate for newborns, can be inaccurate if earwax blocks the sensor or the ear canal is curved, risk of improper insertion.

Pacifier Thermometers

These measure temperature while the baby sucks on a pacifier. They're designed specifically for babies and take about 3 minutes.

Pros: Baby-friendly, non-invasive, easy to use.

Cons: Less accurate than rectal thermometers, slower than digital or infrared options.

Avoid These Thermometers

Mercury thermometers: These are no longer recommended due to the risk of mercury exposure if broken.

Glass alcohol thermometers: Can break and are difficult to read accurately.

Temperature-Taking Methods by Age

Newborns (Birth to 3 Months)

Best method: Rectal temperature with a digital thermometer.

Rectal readings are most accurate for newborns. Insert the thermometer gently into the rectum about ½ inch (1.25 cm). Hold it in place for 30-60 seconds until it beeps.

Axillary (underarm) readings can be used but are less reliable. Forehead and ear thermometers are not recommended for this age group due to lower accuracy.

Infants (3-12 Months)

Best method: Rectal or axillary temperature with a digital thermometer.

Rectal remains the most accurate. Axillary (underarm) temperatures become more feasible, though still less accurate than rectal. Ear thermometers may be used but require careful insertion.

Toddlers (1 Year and Older)

Best methods: Axillary, ear, or forehead thermometers; oral (if child can cooperate).

As children grow, more methods become practical. Many parents switch to forehead or ear thermometers for convenience, though axillary remains reliable.

How to Take Temperature by Method

Rectal Temperature (Most Accurate)

1. Use a digital rectal thermometer (not mercury)
2. Apply a small amount of lubricant like petroleum jelly to the tip
3. Place your baby on their back or belly on a safe surface
4. Gently insert the thermometer about ½ inch into the rectum—never force it
5. Hold it in place for 30-60 seconds until it beeps
6. Remove gently and read the temperature
7. Clean the thermometer with soap and warm water after each use

Axillary Temperature (Underarm)

1. Undress your baby's upper body or lift their shirt
2. Place the thermometer tip in the center of the underarm
3. Hold their arm against their body to keep the thermometer in place
4. Keep still for 30-60 seconds until it beeps
5. Remove and read the temperature

Forehead Temperature (Temporal Artery)

1. Make sure the baby's forehead is dry
2. Gently press the thermometer sensor against the center of the forehead
3. Slowly slide it toward the temple area while holding it in contact with skin
4. Read the temperature after it beeps (usually 1-3 seconds)

Ear Temperature

1. Make sure the baby's ear is clean and free of earwax
2. Gently pull the ear back slightly to straighten the ear canal
3. Insert the thermometer probe gently into the ear canal until snug—don't force
4. Wait for it to beep and read the temperature

Normal Temperature Ranges

Normal body temperature varies slightly by measurement method:

• Rectal: 97.9–100.4°F (36.6–38°C) — most accurate baseline
• Oral: 95.9–99.5°F (35.5–37.5°C)
• Axillary (underarm): 94.5–99.1°F (34.7–37.3°C)
• Forehead/Temporal: 96.4–100.4°F (35.8–38°C) — varies greatly
• Ear: 97.5–99.7°F (36.4–37.6°C)

A rectal temperature of 100.4°F (38°C) or higher is considered a fever in babies under 3 months. For older babies, a temperature of 101°F (38.3°C) or higher is typically considered a fever, though individual variation exists.

When to Call a Doctor

Newborns (0-3 Months)

• Any rectal temperature of 100.4°F (38°C) or higher
• Temperature below 96.8°F (36°C) — indicates hypothermia
• Call immediately—fever in newborns requires medical evaluation

Infants (3-6 Months)

• Rectal temperature of 101°F (38.3°C) or higher, especially with symptoms
• Fever lasting more than 24 hours
• Accompanying symptoms: difficulty feeding, rash, lethargy, irritability

Older Babies and Toddlers

• Temperature of 103°F (39.4°C) or higher
• Fever lasting more than 3 days
• Fever with unusual symptoms: rash, stiff neck, difficulty breathing, severe lethargy

Tips for Accurate Temperature Reading

• Wait after activity: Don't take temperature immediately after vigorous play, warm baths, or feeding. Wait 15-20 minutes.
• Room temperature: Extreme room temperature can affect readings, especially forehead thermometers. Take temperature in a neutral environment.
• Calibrate regularly: Check your thermometer's accuracy by testing on yourself or a trusted baseline.
• Keep still: Movement during temperature-taking reduces accuracy. Distract or soothe your baby while taking their temperature.
• Take multiple readings: If the reading seems off, take another temperature in a few minutes to confirm.
• Know your thermometer: Different thermometers may read slightly differently. Stick with the same one when possible.
• Clean properly: Always clean the thermometer before use and after each use to prevent contamination.

Final Thoughts

Knowing how to take your baby's temperature accurately is an important parenting skill. For newborns and young infants, rectal temperatures with a digital thermometer remain the most reliable method. As your baby grows, you have more options. The key is understanding which method is most appropriate for your child's age and using proper technique. When in doubt about fever or any health concern, contact your pediatrician. They're the best resource for interpreting temperature readings in the context of your baby's overall health.