Formula preparation and storage:
the guidance does not agree.
One question, several official answers, each with a written reason. This page does not choose between them. It shows you who says what, why they say it, and the large part where all of them say exactly the same thing.
Important: This page is general information and does not replace medical advice, diagnosis or treatment. Beluna is a record-keeping tool; it gives no health recommendations, builds no feeding plan and makes no diagnosis. Which formula your baby has, how much, and how it is prepared is a decision you make with the health professional who sees your baby.
Everything here is taken from the public bodies named under References: the joint WHO/FAO guidelines, the US Centers for Disease Control and Prevention, the German Gesund ins Leben network, France's ANSES, the Spanish Association of Paediatrics, Brazil's ANVISA and Japan's Ministry of Health, Labour and Welfare. No other sources were used.
Who says what
Powdered infant formula is not a sterile product. That is the one starting point every body below shares. What they disagree about is what to do with that fact: how hot the water should be, and whether a bottle may be made in advance.
| Body | Water | May bottles be made ahead? |
|---|---|---|
| WHO / FAO (2007 guidelines) | Boiled water, no less than 70 °C | “It is best to make PIF fresh for each feed.” If made ahead, cool quickly and refrigerate |
| CDC (United States) | For most babies, tap water and the label instructions. For a baby under 2 months, born preterm, or with a weakened immune system: boil the water, wait about five minutes, then mix | If not used within 2 hours of preparation, refrigerate |
| Gesund ins Leben (Germany, BZfE network) | Fresh tap water, lukewarm, at most 40 °C — the stated reason is scalding | No. “Prepared fresh before the meal”; formula that is not drunk is discarded, never kept or re-warmed |
| ANSES (France) | Cold tap water (below 25 °C); run the tap for a moment first | Yes. In the coldest part of the fridge, at 4 °C or below |
| AEP (Spanish Association of Paediatrics) | Tap water where the public supply is well controlled, or low-mineral bottled water; “lukewarm rather than hot” | Yes. If needed, the whole day's bottles may be made, provided they are kept in the fridge |
| ANVISA (Brazil) | The dilution on the label and “a safe temperature (70 °C)” | — |
| Ministry of Health (Japan) | Water boiled and held at 70 °C or above | — |
Why they disagree
This is not a translation artefact, and it is not one body being behind the others. They are ranking two different risks.
The WHO's reason is a bacterium. Cronobacter — called E. sakazakii in the guidelines — can survive in the dry powder and cause rare but severe illness in newborns. The guidelines state it plainly: preparing formula with water at no less than 70 °C dramatically reduces the risk. Shortening the time between preparation and feeding does the same, as does keeping prepared feed no warmer than 5 °C.
Germany's reason is scalding. Gesund ins Leben asks for water that is lukewarm, at most 40 °C, and says why: to avoid burning the baby's mouth. It can do without the hot-water kill step because the same recommendation carries a second rule — make it fresh for every feed, give it immediately, throw away what is left. The bacteria are never given time to multiply.
The CDC sits between the two and splits the answer by the baby. For most babies it treats tap water and the manufacturer's instructions as sufficient. But its “extra precautions” section — for babies younger than 2 months, born before 37 weeks, or with a weakened immune system — describes boiling the water and waiting about five minutes, which is the WHO method in practice. If your baby is in one of those three groups, all three bodies land in the same place.
This page does not pick a winner. Which one applies to your baby is a conversation with the health professional who knows their history; our job here is to show that both answers exist and what each rests on.
Where all of them agree
The disagreement is confined to water temperature and making bottles ahead. On every other step the guidance is the same everywhere:
- Clean hands and a clean surface first; bottles and teats washed.
- Water first, then powder. The water always goes into the bottle before the scoops.
- Never change the ratio on the label. Too much water leaves the feed short of what your baby needs; too little makes the kidneys and gut work too hard.
- Use the scoop that came with the tin, keep it dry, and throw it away with the tin.
- Never a microwave. It heats unevenly and leaves hot spots that scald. Warm the bottle under running warm water instead.
- Test on your wrist — it should feel warm, not hot.
- Throw away what the baby does not finish. Formula mixed with saliva is a place bacteria grow.
- An opened tin does not go in the fridge — a cool dry place, lid closed. The CDC says most formulas need to be used within one month of opening and that the label gives the exact figure.
How long prepared formula keeps
The times differ a little between bodies. The table gives each one's own published figure, unchanged.
| WHO / FAO | CDC | ANSES | |
|---|---|---|---|
| At room temperature | 2 hours, then discard | 2 hours from preparation | 1 hour, then discard |
| Once feeding starts | Discard anything not consumed within two hours | 1 hour | 30 minutes once warmed |
| In the fridge | Up to 24 hours at no higher than 5 °C | 24 hours | Coldest part, 4 °C or below |
| What the baby leaves | Discard | Discard | Discard |
Germany is absent from this table because Gesund ins Leben does not recommend storing prepared formula at all: fresh each feed, the rest thrown away.
Three common mistakes
- Keeping a made-up bottle in a flask or a bottle warmer. The AEP warns about this by name: prepared bottles must not be kept in flasks or warmers. The thing you keep warm is the water — the powder goes in just before the feed. A warm bottle standing for hours is close to an incubator.
- Warming in a microwave. The liquid heats unevenly and scalding hot spots remain inside; shaking the bottle does not reliably fix that.
- Putting an opened tin in the fridge. The CDC says not to; moisture makes the powder clump. Writing the opening date on the lid is the easiest way to keep to the one-month rule.
The CDC position in full
Because the American guidance is the one that splits by risk rather than giving a single rule, it is worth reading in its own words. The CDC says that most of the time it is safe to prepare powdered formula by mixing it with tap water, filtered or unfiltered, following the manufacturer's instructions on the container.
It then names three groups for whom that is not enough: babies younger than two months, babies born before 37 weeks of pregnancy, and babies with a weakened immune system. For these, the instruction is to boil the water and wait about five minutes before mixing — the formula will then be too hot to feed, so it has to be cooled and checked on your wrist before it reaches the baby.
Read alongside the WHO guidelines, this is the same intervention with a narrower target population, not a different piece of science.
What Beluna does — and does not do
Beluna does not tell you how much to feed. It records what you fed: the bottle with its time and its millilitres, expressed milk drawn down from your stock, each batch with its own expiry. You do not have to remember at 3am which bottle this is — it is already in the record.
You will not find a portion table, a feeding plan or a temperature recommendation here. We do not print a number we cannot show a source for.
Beluna
Beluna does not recommend an amount
It records the one you gave: the bottle with its time and millilitres, expressed milk drawn down from your stock, every batch with its expiry date.
Beluna gives no medical advice, makes no diagnosis and recommends no portion.Frequently asked questions
How hot should the water be?
There are two official answers. The joint WHO/FAO guidelines call for water no cooler than 70 °C, because Cronobacter can survive in the dry powder. Germany's Gesund ins Leben network calls for lukewarm water at most 40 °C to avoid scalding, and in exchange requires every feed to be made fresh. The CDC sits between them: tap water is enough for most babies, but for a baby under two months, born preterm, or immunocompromised it asks you to boil the water and wait about five minutes.
Can I make bottles up in advance for the night?
It depends which body you follow. France's ANSES and Spain's AEP both say yes, refrigerated — ANSES specifies 4 °C or below, the AEP says the whole day's bottles may be made. Germany's Gesund ins Leben says no; each feed must be made fresh. The WHO says fresh is best, but also describes how to do it ahead: cool quickly and keep for up to 24 hours in a fridge no warmer than 5 °C.
Can I keep what my baby did not finish?
No — and this is one of the points where every body agrees without exception. Formula mixed with your baby's saliva is a place bacteria grow. What is left in the bottle is thrown away and the bottle is cleaned before its next use.
How long does an opened tin last?
The CDC says most formulas need to be used within one month of opening, and that the label carries the exact figure. Keep the tin in a cool, dry place with the lid closed — not in the fridge. Writing the date you opened it on the lid is the practical way to track the month.
Why not warm formula in the microwave?
A microwave heats unevenly and leaves hot spots that can burn your baby's mouth and throat. The CDC rules it out directly. If you want to warm a bottle, hold it under running warm water and put a few drops on your wrist before feeding.
Does Beluna tell me how much formula to give?
No. Beluna is a record-keeping tool: it logs the bottle with its time and millilitres, draws expressed milk down from your stock and tracks each batch's expiry. It does not suggest a portion, build a feeding plan, or recommend a temperature or a brand.
References
Everything on this page comes from the public bodies listed below. Every link was opened and its content checked in September 2026. Guidance is revised over time; where this page and a source disagree, the source is right.
- World Health Organization (WHO) and FAO — “Safe preparation, storage and handling of powdered infant formula: guidelines”. https://www.who.int/publications/i/item/9789241595414
Source of the “no less than 70 °C” figure, the two-hour room-temperature limit, 24 hours at no higher than 5 °C, and “it is best to make PIF fresh for each feed” - Centers for Disease Control and Prevention (CDC) — “Infant Formula Preparation and Storage”. https://www.cdc.gov/infant-toddler-nutrition/formula-feeding/preparation-and-storage.html
Water before powder, the microwave prohibition, the 2 hour / 1 hour / 24 hour limits, one month for an opened tin, and the extra precautions for babies under 2 months, preterm or immunocompromised - Gesund ins Leben network — Bundeszentrum für Ernährung (BZfE) — “Zubereitung der Säuglingsmilchnahrung”. https://www.gesund-ins-leben.de/fuer-fachkreise/bestens-unterstuetzt-durchs-1-lebensjahr/handlungsempfehlungen/saeuglingsmilchnahrung/zubereitung-der-saeuglingsmilchnahrung/
Source of “lukewarm, at most 40 °C” and of the rule that every feed is made fresh and leftovers discarded - ANSES — French Agency for Food, Environmental and Occupational Health Safety — “Biberon : comment le préparer et le conserver ?”. https://www.anses.fr/fr/content/biberon-comment-le-preparer-et-le-conserver
Cold tap water, 4 °C or below in the fridge, one hour at room temperature and thirty minutes once warmed - Asociación Española de Pediatría (AEP) — En Familia — “Preparando el biberón”. https://www.aeped.es/enfamilia/salud-en-familia/preparando-biberon
One level scoop per 30 ml, the whole day's bottles refrigerated, and the warning against keeping prepared bottles in flasks or warmers - ANVISA — Brazilian Health Regulatory Agency — “Anvisa orienta sobre uso seguro de fórmulas infantis”. https://www.gov.br/anvisa/pt-br/assuntos/noticias-anvisa/2024/anvisa-orienta-sobre-uso-seguro-de-formulas-infantis
Source of “a safe temperature (70 °C)” against contamination by Cronobacter and Salmonella - Ministry of Health, Labour and Welfare, Japan — “乳児用調製粉乳の安全な調乳、保存及び取扱いに関するガイドラインについて”. https://www.mhlw.go.jp/topics/syokuchu/kanren/kanshi/070605-1.html
The WHO/FAO guidelines as applied in Japan: the water used is to be held at 70 °C or above