A lot of baby feeding content is written as though breastfeeding is the default and everything else is a footnote. It isn't. Around half of UK parents are using formula by the time their baby is 6 weeks old. Many more are doing both.
This guide is for them.
Formula feeding: what matters
If you are formula feeding, the single most important thing you can do is prepare it safely. Formula is not sterile. It needs to be made with water hot enough (70°C or above) to kill any bacteria in the powder, even if the tin looks clean.
Safe preparation:
- Boil fresh tap water and allow it to cool for no more than 30 minutes (so it stays above 70°C)
- Pour the required amount of water into a sterilised bottle
- Add the exact number of scoops of powder, levelled off, not packed
- Put the lid on and shake well
- Cool quickly by holding under cold running water
- Test the temperature on your wrist before feeding
Pre-made ready-to-feed formula is sterile and doesn't require this process. It's more expensive but useful for nights and when you're out.
What you cannot do:
- Make bottles in advance and store them at room temperature
- Reheat a bottle a baby has already started
- Use water below 70°C to make up formula
- Alter the scoops ratio to stretch the tin further
Which formula to use
Most formula brands available in the UK are regulated to the same nutritional standard. Own-brand supermarket formulas meet the same requirements as premium brands. The differences are mostly in marketing.
First infant formula is appropriate from birth and for the full first year. You don't need to switch to "follow-on" (stage 2) formula at 6 months. Follow-on formula exists primarily as a marketing category, it is not clinically necessary.
Specialist formulas (for reflux, colic, lactose intolerance, or cow's milk protein allergy) should be prescribed or recommended by a GP or health visitor rather than chosen independently. CMPA in particular requires a properly hydrolysed formula that is prescription-only.
Don't switch formulas repeatedly trying to solve unsettled behaviour unless you have clear clinical reasons. Most unsettled behaviour in newborns isn't caused by the formula.
How much formula: a rough guide
Approximate daily volumes by age:
- 0–4 weeks: around 150–200ml per kg of body weight per day, split across feeds
- 1–2 months: most babies take 120–150ml per feed, around 6–8 times a day
- 3–4 months: 150–180ml per feed, 5–6 times a day
- 6 months onwards: up to 210ml per feed, reducing as solids are introduced
These are guides, not rules. Babies vary significantly. Feed responsively rather than by the clock.
Combination feeding
Combination feeding (using both breast and formula) is common and workable, though it does require some adjustment.
Why parents choose it:
- To share feeding with a partner overnight
- To give a breastfed baby a supplement if supply is low or weight gain is slow
- To return to work while continuing to breastfeed
- Because exclusive breastfeeding isn't sustainable for them
What to know:
- Introducing formula can reduce your milk supply over time, especially in the early weeks when supply is still being established. This isn't inevitable, but it's worth being aware of.
- If you want to maintain breastfeeding as much as possible, try to replace formula feeds with expressed milk where you can, or increase feeding frequency to compensate.
- By 6–8 weeks, supply is more established and combination feeding is easier to manage without affecting breastfeeding significantly.
- There is no clinical evidence that combination feeding "confuses" babies. Nipple confusion is a disputed concept, and most babies move between breast and bottle without difficulty if introduced carefully.
Bottle feeding a breastfed baby
Paced bottle feeding reduces the risk of bottle preference and helps a breastfed baby manage the flow:
- Hold the bottle horizontally (not tilted down) so milk only flows when the baby actively sucks
- Use a slow-flow teat
- Feed in a semi-upright position
- Pause halfway through and allow the baby to pace the feed
On guilt
This guide won't tell you how to feed. That's your decision, made in the context of your body, your mental health, your support network, your return to work, and what's sustainable for you.
Formula has been safe, regulated, and nutritionally complete for decades. Breastmilk has advantages. A parent who is well-supported and not depleted is a significant advantage too.
If you're combination feeding out of necessity or choosing formula from the start, you are not doing less for your baby. You're feeding your baby.
If you have concerns about weight gain, feeding volume, or your baby's behaviour around feeds, your health visitor or GP is the right first contact.