Normal Newborn Temperature: How to Check and When to Get Help

The short answer

A newborn's temperature is not one fixed number. The NHS describes about 36.4°C as a typical temperature for babies and children, with some variation; the reading also depends on how it is measured. A temperature of 38°C (100.4°F) or higher in a baby under three months needs immediate medical assessment. An unusually low temperature or an unwell-looking baby also needs prompt attention, even without a fever.

If your newborn already has a concerning reading, seek help now rather than working through the whole article. This guide explains the numbers and how to give a clinician useful information; it cannot determine whether your baby is well.

Why different “normal” numbers appear online

Temperature readings depend on the measurement site, device, and circumstances. A number from under the arm is not interchangeable with a rectal reading. The NHS's temperature guide describes its approach using a digital thermometer in the armpit, while US AAP guidance gives particular weight to rectal measurements in young infants.

This is why a single universal “normal newborn range” can be misleading. When you ask about a number, include where and how you measured it. Do not simply compare it with a chart that may assume a different method.

For example, “37.5°C under the arm using a digital thermometer” is more informative than “a little high.” It still does not answer whether the baby is well, but it gives the professional a clear starting point. Report the displayed value rather than adding or subtracting a degree yourself.

Which thermometer method should you use?

Follow the instructions from your local health service and your baby's clinician. There are meaningful regional differences:

• UK: the NHS recommends a digital armpit measurement for children under five.
• US: the AAP describes rectal measurement as the most accurate for infants, especially under three months. Ask your pediatrician how they want you to check a newborn and demonstrate the technique if needed.

Do not change methods repeatedly in search of the lowest number. If a reading is concerning or seems inconsistent with how your baby looks, contact a clinician and explain what you have measured.

The AAP advises that ear thermometers are unreliable below six months because the ear canals are too narrow. Forehead strips and a hand on the forehead are not reliable substitutes for a thermometer. A wearable or room thermometer also does not replace an appropriate body-temperature measurement.

If you are unsure which device you own, look at its instructions before using it. A device intended for one site should not be improvised for another. Keep it clean according to the manufacturer's directions, and keep the device and any spare batteries out of children's reach.

Taking an armpit reading using the NHS approach

Hold your baby securely and comfortably, with their head and neck supported. Put the digital thermometer in the armpit and gently keep the arm against the body for the time specified by the device instructions. Record the result and the measurement method.

Recent bathing, heavy wrapping, or a very warm room can affect a reading. The NHS suggests allowing a few minutes before rechecking in those circumstances, without making the baby cold or shivery. Do not use possible overheating as a reason to delay help for a newborn with a fever or concerning symptoms.

Have the information ready to share: baby's age, reading, unit, method, and time. If someone else takes the next reading, ask them to record the same details so you are not comparing unlike measurements.

The method recommended to your family may differ from this example. If your care team has provided a specific plan, follow it and tell them about any reading that concerns you.

When a high temperature needs immediate attention

The AAP says to call the pediatrician immediately for a baby three months or younger with a rectal temperature of 38°C or above, even if there are no other symptoms. The cause needs assessment; a cheerful-looking baby should not be assumed safe simply because they are not crying.

For a newborn with a reading of 38°C or higher, seek immediate medical assessment through your local urgent or emergency service. In the UK, current NHS urgent-help guidance directs parents to A&E or 999 for this situation. Elsewhere, contact the pediatrician immediately and use emergency care if prompt assessment is unavailable.

An underarm reading below 38°C does not rule out fever or serious illness. The AAP notes that underarm measurements may use a lower fever threshold. Tell the clinician the exact value and method, especially if your baby seems unwell.

Do not wait until morning, wait for a second symptom, or postpone the call while trying to make the temperature fall. Ask the clinician before giving fever medicine to a newborn; the priority is getting the baby assessed.

A low reading matters too

The NHS identifies a temperature below 36°C (96.8°F) as a possible sign of serious illness. Get immediate medical advice for a newborn with a very low reading. If they are difficult to wake, breathing abnormally, or appear seriously unwell, use emergency services immediately.

You can report an uncertain measurement without first solving the uncertainty at home. Say, “The thermometer showed this, I used it this way, and this is how the baby looks.” The clinician can guide any repeat measurement while arranging the appropriate assessment.

Avoid treating the number with a hot water bottle, heating pad, or a pile of bedding. A low body temperature needs an explanation; making the environment hotter is not a substitute for checking the baby.

Look at your baby as well as the thermometer

Get emergency help for breathing difficulty, blue or grey skin, a seizure, or a baby who cannot be woken normally. The NHS warning signs apply even without a high reading. Do not let a number that looks reassuring override a worrying change in the baby.

If feeding is reduced or wet nappies are fewer than usual, tell a clinician promptly. Our guide to water and infant hydration explains why an extra water bottle is not a general solution for a young baby who may be unwell.

Body temperature and bedroom temperature are separate questions. Our sleep-clothing guide covers the sleep environment, but a comfortable room cannot confirm that an infant is free of illness. Likewise, sleep logs should not be used to label unusual drowsiness as a successful longer nap.

A short note for the medical call

You can use these prompts without delaying the call to fill every gap:

• How old is your baby, and were they born prematurely?
• What did the thermometer display, in which unit, and at what time?
• Where was the temperature measured, and with which type of device?
• How are feeding, waking, breathing, and nappies different from usual?
• Has a clinician given an individual care plan or has anything else changed?

If you do not know an answer, say so. An approximate observation is better than inventing a precise one. If possible, have another adult gather the notes while you make the call, but being alone is not a reason to wait.

Common questions

Is 37°C automatically a fever?

No. The method and the baby's condition matter. Give the actual reading to a clinician if you are concerned; do not use one number as a guarantee of either illness or safety.

Should I use the same fever advice as for an older sibling?

No. Young infants need a different level of caution. Advice about watching an otherwise well older child's fever at home should not be transferred to a newborn.

Can I wait because my baby is still feeding?

Not when a newborn has a concerning temperature or emergency symptoms. Feeding at one moment does not remove the need for immediate assessment.

Sources checked September 30, 2026. General education from the Bambii Editorial Team; not individually reviewed by a clinician. Read our editorial standards or send a correction to team@bambii.app. Cover illustration generated with AI.