Can you warm a glass baby bottle?

Overview

Yes, you can warm a glass baby bottle. Do it gently: stand it in a bowl of warm water or use a bottle warmer, then test a few drops on your wrist. Never put any bottle in the microwave.

You might not need to warm it at all. The CDC says breast milk and infant formula don’t need to be warmed, so if your baby takes milk cold or at room temperature, that’s fine. [1]

Optional Warm milk only if your baby prefers it. [2]

Gentle heat Warm water or a bottle warmer, for a few minutes. Check the milk, not the dial.

Never The microwave or the stove. Both can heat milk unevenly, leaving hot spots that burn your baby’s mouth. [2]

Does milk need to be warm?

No. The CDC says breast milk can be served at room temperature or cold, and that formula doesn’t need warming. [1] [2] The FDA agrees on formula. [3] Under the national standards for child care, bottles can be served cold from the refrigerator. [4]

Babies differ, though. The Academy of Breastfeeding Medicine notes that most infants drink milk cool, at room temperature or warmed. [5] If yours takes it cool, skip the warming. That’s one less job at 3 am.

Using a bottle warmer

A bottle warmer does the same job with less watching. Follow its instructions, including any setting for glass. Then test the milk on your wrist anyway, every time.

Don’t trust the setting on its own. In a 2015 lab simulation, some warming methods took milk well above body temperature. [6] The Academy of Breastfeeding Medicine suggests warming breast milk slowly, in lukewarm water no hotter than 40°C (104°F). [5]

Thawing frozen breast milk

The CDC gives three ways to thaw: overnight in the fridge, in a bowl of warm or lukewarm water, or under lukewarm running water. Use the oldest milk first. [1]

Source: CDC, Breast Milk Storage and Preparation. [1]

Why never the microwave

Microwaves heat milk unevenly. The bottle can feel cool in your hand while a pocket of milk inside is hot enough to burn your baby’s mouth and throat. [2]

Microwaving can also destroy nutrients in breast milk, the CDC says, [1] and the AAP is blunt: microwaving breast milk isn’t safe. [7] Glass or plastic, same answer.

Glass and temperature changes

Borosilicate glass copes well with warm water and boiling. When heated, it expands about a third as much as ordinary soda-lime glass, [8] and it’s what many glass baby bottles are made of, ours included.

It’s still glass. Avoid sudden jumps, like freezer straight into very hot water, and follow your bottle maker’s instructions.

Look the bottle over before every use. If it’s chipped or cracked, stop using it. The CDC advises throwing bottles away at the first sign of damage or wear, [9] and the AAP notes that glass bottles carry a risk of injury if dropped or broken. [10]

Which Ronini bottle to warm

We made The Glass Bottle for warming. It’s plain borosilicate glass with no silicone layer, so warm water reaches the glass directly and the milk warms faster than in a wrapped bottle.

The Wrapped Glass Bottle has food-grade silicone shaped around the glass, and it works in a bottle warmer or a warm-water bath too. With either one, follow the instructions and avoid sudden temperature extremes.

Bottles

The Glass Bottle

Bare borosilicate glass for everyday feeds at home. Easy to see through, with the same soft nipple and interchangeable parts as the Wrapped Glass...

From $40

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Disclosure This guide is published by Ronini, and The Glass Bottle and The Wrapped Glass Bottle are our products. The warming and storage guidance comes from the CDC, FDA, AAP and the other sources listed below, and it applies to any bottle.

Frequently asked questions

References

General information, not medical advice. Your pediatrician knows your baby best. Last reviewed October 11, 2026.