How to Make Formula Safely, Store It and Sanitize Bottles (CDC)

Three forms of formula

• Powder: cheapest and most common. It is not sterile, so preparation matters most.
• Liquid concentrate: sterile until opened; mixed with water, usually in equal parts. Follow the label exactly.
• Ready-to-feed: no mixing, and sterile until opened. Liquid formula, especially ready-to-feed, is the lower-risk choice for babies born early, under 2 months, or with weakened immune systems. Refrigerate after opening and use within the time on the label.

Mixing powder, step by step

1. Wash your hands, clean the counter and check the use-by date.
2. Measure the water into a clean bottle first, then add powder.
3. Use only the scoop from that container. Fill it loosely and level it with a clean straight edge; don't pack it down.
4. Use the exact ratio on the label (many are 1 level scoop per 2 oz / 60 mL of water, but check).
5. Cap and shake or swirl until fully mixed.
6. Never add extra water to stretch formula. Watered-down formula can cause dangerously low sodium, seizures and poor growth. Too little water strains the kidneys and dehydrates.
7. Never use homemade formula, cow's milk, goat's milk, plant milks or toddler formula before 12 months.

Water

• Safe tap water, fluoridated or not, is fine for most babies. Use cold tap water, not hot.
• On a private well, have the water tested (especially for nitrates) before using it, and yearly.
• If you're unsure about your water, boil it for 1 minute (3 minutes above 6,500 feet), then cool.
• For babies under 2 months, born before 37 weeks or with weakened immunity, CDC and WHO suggest an extra step with powder: mix it with water that is still at least 158°F (70°C), which usually means within about 5 minutes of boiling, then cool the bottle quickly under cold running water before feeding.

Warming

• Warming isn't needed. If your baby prefers it warm, stand the bottle in warm water for a few minutes, swirl, and test a few drops on your wrist. Never microwave: it heats unevenly and can scald.

Storage and timing

• Use prepared formula within 2 hours, or within 1 hour once the baby starts drinking. Throw out what's left; saliva lets germs grow.
• Bottles mixed ahead go straight into the fridge and must be used within 24 hours.
• Don't freeze formula. Keep powder closed in a cool, dry place and follow the label on how long an opened container lasts (often about 1 month).
• Nights and outings: carry pre-measured powder and safe water separately and mix when needed, use ready-to-feed, or keep mixed bottles in a cooler with ice packs.

Cleaning and sanitizing

• After every feed, take the bottle apart (nipple, ring, valve, cap). Rinse under running water.
• Wash in a clean basin used only for feeding items (not straight in the sink) with hot, soapy water and a bottle brush, or in a dishwasher with hot water and a heated dry cycle if parts are dishwasher-safe.
• Let everything air-dry on a clean rack or towel; don't wipe dry with a dish towel.
• CDC suggests sanitizing at least once a day, and it matters most for babies under 2 months, born preterm or with weakened immunity. For older healthy babies, careful cleaning after every use may be enough. To sanitize: boil parts for 5 minutes, use a steam sanitizer, or soak at least 2 minutes in 2 teaspoons of unscented bleach per gallon (16 cups) of water, then air-dry without rinsing. Sanitize new bottles before first use.

Shortages and recalls

• Check recalls by the lot number on the can. Avoid online auctions and unregulated imports.
• In a shortage, don't dilute or make formula at home. Ask the pediatrician, WIC or a local food bank about a comparable formula; most standard formulas can be swapped (see the choosing formula guide).

When to check in

Call the pediatrician the same day if: - A baby under 3 months has a temperature of 100.4°F (38°C) or higher, or is feeding poorly, unusually sleepy or irritable, or grunting. - You realize formula was mixed too watery or too strong and the baby seems unwell. Call 911 for a seizure or a baby who is hard to wake.