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us Health & medical scares newborn fever • infant under 3 months fever • baby 100.4 fever • rectal temp 100.4 • infant feels hot • baby unusually sleepy • newborn hard to wake • lethargic infant • too sleepy to feed • under 12 weeks temperature • newborn drowsy sick • fever after shots infant • baby not acting right • newborn emergency fever • worried newborn fever • under 90 days fever • infant fever threshold • sleepy baby and fever

What to do if…
an infant under three months has a fever or feels unusually sleepy

Short answer

This is urgent in a baby under 3 months. If your baby has a temperature of 100.4°F (38°C) or higher or is unusually sleepy/hard to wake, call your pediatrician immediately—and if they’re hard to wake, very floppy, or struggling to breathe, call 911 or go to the ER now.

Do not do these things

  • Do not “watch and wait” with a very young infant who has fever or marked sleepiness.
  • Do not rely on touch or a forehead strip alone.
  • Do not use cold baths, ice, or rubbing alcohol.
  • Do not overdress or tightly bundle them.
  • Do not give aspirin.
  • Do not give ibuprofen to a baby under 6 months unless your child’s doctor tells you to.
  • Do not delay urgent care while trying multiple home remedies.

What to do now

  1. Get to a calm, safe pause. Put your baby on a firm, flat surface (or hold them securely) so you can observe breathing and responsiveness.
  2. Go to emergency care now (call 911 or go to the ER) if any apply:
    • Hard to wake or not responding normally, very floppy/limp, or you’re struggling to keep them awake
    • Trouble breathing (working hard, grunting, very fast breathing, long pauses, bluish lips/skin)
    • Seizure, or your baby looks rapidly worse
  3. Check a temperature if you can (but don’t delay emergency care if they look very unwell).
    • For young infants, rectal temperature is commonly used as the accuracy standard. If you’re not comfortable doing that, take the temperature the safest way you can and tell the clinician how you measured it.
    • If any method shows 100.4°F (38°C) or higher, treat it as a fever in this age group.
  4. If the temperature is 100.4°F (38°C) or higher: get immediate clinical direction.
    • Call your pediatrician right away (including after-hours).
    • If you cannot reach them immediately, or you’re told to be seen urgently, go to the ER. (Many clinicians advise ER evaluation for fever in very young infants, especially under 2 months.)
  5. If the main issue is “unusually sleepy” even without a confirmed fever, treat it as urgent.
    • If your baby is too sleepy to feed normally, “not acting right,” or much harder to wake than usual, call the pediatrician now; if difficult to awaken, choose 911/ER.
  6. While you’re getting help, do simple supportive steps:
    • Keep them lightly dressed in a comfortable room.
    • Offer feeds as usual; don’t force. Note how much they take.
    • Count wet diapers today (fewer than usual can matter) and note any vomiting/rash/breathing changes.
  7. Prepare a 60-second summary for the clinician (write it down):
    • Age in weeks; highest temp + time; how you took it; how sleepy/alert they are;
    • Feeding changes; wet diapers; vomiting/rash/breathing changes;
    • Recent vaccines (and when); any meds already given (name/time); any medical issues.
  8. If you’re told to go in, go promptly and bring essentials:
    • Insurance card (if you have it), diapers/wipes, a blanket, and your notes.

What can wait

  • You do not need to figure out the exact cause right now.
  • You do not need to try to “break” the fever at home before contacting a clinician.
  • You do not need to decide about tests or treatments—focus on rapid medical assessment.

Important reassurance

It makes sense to feel alarmed by fever or unusual sleepiness in a very young infant. Getting same-day help is the safest choice, and clinicians expect these calls.

Scope note

These are immediate first steps to reduce risk and get the right level of care quickly. Follow your clinician’s instructions for next steps.

Important note

This is general information, not medical advice for a specific child. If your baby seems to be getting worse, is hard to wake, or is having trouble breathing, seek emergency care right away.

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