Mixed (powdered) formula is generally safe for about 2 hours at room temperature if your baby has not started drinking from the bottle, and only about 1 hour once your baby has drunk from it (because of saliva and bacteria).

Quick Scoop

  • Unused mixed formula at room temp: up to 2 hours is the usual guideline.
  • Once baby has started drinking: use within 1 hour, then toss.
  • Mixed formula in the fridge (baby hasn’t drunk from it): up to 24 hours in a closed container.
  • If you’re ever unsure or it’s been sitting longer than this, it’s safer to throw it away.

Why the timing matters

Once powder and water are mixed, bacteria can start to grow, especially at room temperature, which is why most medical and parenting sources stick to the 2‑hour rule for untouched formula and 1 hour after feeding has started. Some caregivers and midwives mention longer times (like 4–6 hours), but this is more relaxed than the standard safety guidance and carries more risk, particularly for newborns.

Practical example

  • You mix a bottle at 10:00 and baby hasn’t touched it: aim to use or refrigerate it by around 12:00.
  • Baby starts drinking at 10:15 and leaves some: discard what’s left by about 11:15.
  • If you know you’ll need bottles later, you can pre‑mix and refrigerate them, then use within 24 hours, warming if desired.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.