Formula feeding guide: safe preparation, amounts and tips

Choosing and preparing formula safely

Use a first infant formula that is suitable for your baby's age, and always follow the manufacturer's instructions on the tin. Powdered formula is not sterile, so how you prepare it matters. Wash your hands, and clean and sterilise bottles and teats, at least for the first months. Use the exact amount of water and powder specified: too little water can overload a baby's kidneys, and too much dilutes the nutrition.

Many authorities, including the WHO and the NHS, advise using freshly boiled water that has cooled but is still hot (at least about 70 degrees) to mix powder, then cooling the bottle under cold running water before feeding. Always follow the instructions on your specific product, as they vary. Test the temperature on the inside of your wrist: it should feel lukewarm, not hot. Avoid microwaving bottles, as hot spots can burn.

Leftovers and storage

Bacteria multiply quickly in prepared formula. As a general rule, use a made-up bottle soon after mixing it and throw away whatever is left once the feed is over. Do not save milk from a partly finished bottle for later. If you prepare bottles in advance, store them in the back of the fridge and use them within 24 hours, following your product's guidance.

Paced bottle feeding

Paced feeding copies the rhythm of breastfeeding and helps babies recognise when they are full. Hold your baby fairly upright, hold the bottle roughly horizontal so milk does not pour in, and let your baby draw the teat in. Pause every few sucks, tipping the bottle down to give breaks, and switch sides halfway through, as you would at the breast.

Watch for hunger and fullness cues rather than finishing the bottle every time: turning away, slowing down, relaxed hands and falling asleep all mean the feed may be over. A slow-flow teat suits young babies.

How much formula does a baby need?

Amounts vary from baby to baby, so treat these as rough guides. In the first days a newborn takes only small amounts, perhaps 30 to 60 ml per feed, increasing to around 60 to 90 ml per feed in the first weeks, often 8 or more times in 24 hours. By around 2 months, many babies take 120 to 150 ml every 3 to 4 hours, and by 4 to 6 months 150 to 210 ml per feed, 4 to 6 times a day. A common rule of thumb is about 150 ml per kilo of body weight per day, in the first months.

Feed on demand and trust your baby's cues. If your baby is gaining weight steadily, has plenty of wet diapers and seems content, they are getting enough. Your health nurse will track growth with you.

Combining formula with breastfeeding

Many families mix breastfeeding and formula, and that is fine. A top-up bottle can help with low supply, a return to work or a rest for you. Keep in mind that the breast makes milk based on how often it is emptied, so replacing many breastfeeds may reduce supply. If you want to keep breastfeeding, try to keep your regular feeds or pump when you skip one, and introduce a bottle gradually.

Whatever your feeding choice, you are doing a good job. Talk to your health nurse if you want support with mixed feeding, switching or stopping.

When to ask for help

Contact your health nurse or doctor if your baby is not gaining weight, refuses feeds, has fewer wet diapers, vomits forcefully, has blood in the stool, a rash or wheezing after feeds, or severe constipation. Do not change to a different type of formula, or special formulas, without medical advice. If your baby seems unwell or very sleepy, seek care urgently.