This is the thing I mention at almost every visit, and the thing almost nobody has been told clearly. Vitamin D is the one supplement your breastfed baby genuinely needs, from birth, every day, and a great many babies in this country are not getting it. It is not a sign that your milk is lacking. It is simply that none of us make enough vitamin D in a British winter.

What your baby needs

From birth to one year, a breastfed baby should have a daily supplement of 8.5 to 10 micrograms of vitamin D.

That applies:

  • Whether you are breastfeeding exclusively or alongside formula.
  • Whether or not you are taking a vitamin D supplement yourself. Your own supplement does not pass enough into your milk to cover your baby.
  • All year round, not just in winter.

If your baby is having 500ml of formula a day, roughly a pint, they do not need drops, because infant formula already has vitamin D added. If they are having less than that alongside breastfeeding, they still need the drops.

From one to four years, children should carry on with 10 micrograms daily.

What you need

While you are breastfeeding, you should take 10 micrograms of vitamin D a day yourself. This is for your own bones and muscles rather than for your milk. It is easy to forget in the fog of the early weeks, so it is worth keeping it somewhere you will see it, next to the kettle or with your phone charger.

Where to get it, including free

Vitamin drops for babies are sold in pharmacies and supermarkets, and they are inexpensive. Look for drops made for babies from birth, and check the label gives 8.5 to 10 micrograms.

Healthy Start vitamins are free if you are more than ten weeks pregnant or have a child under four and you qualify. If you are eligible you are sent a Healthy Start card. The vitamin drops are suitable from birth to four years. It is worth checking whether you qualify, because a lot of families who are entitled do not realise it.

Why it matters

Vitamin D helps the body absorb calcium, which builds bones and teeth and keeps muscles working. A baby who does not get enough over a long period can develop rickets, which softens and weakens growing bones. It is rare, but it is entirely preventable, and it still happens in the UK.

We make vitamin D in our skin from summer sunlight, roughly late March to the end of September in this country. Outside those months there is not enough strength in the sunlight for anyone here to make it, whatever they do. Babies under six months should also be kept out of direct strong sun altogether, so they cannot rely on sunlight even in summer.

Some people make less vitamin D from the same sunlight than others. If you have brown or Black skin, or if you cover your skin when you are outside, you will make less, so both you and your baby are more likely to be short of it. That is not a reason to change what you wear or how you live. It is a reason to be straightforward about taking the supplement.

Practical bits that trip people up

  • The drops go in the mouth, not in a bottle. Straight onto the tongue or inside the cheek is easiest. Adding them to a bottle risks your baby not finishing it and not getting the full dose.
  • A daily habit beats remembering. Attach it to something you already do, the first nappy change of the day or your morning tea.
  • Missing a day does not undo anything. Just carry on the next day.
  • Do not double up. If you are giving a multivitamin drop that already contains vitamin D, you do not need a separate one as well. Check the label, or ask your pharmacist.
  • Vitamin D is not a supply booster. It will not increase your milk. It is about your baby's bones.

Speak to your health visitor, GP or pharmacist if:

  • You are not sure which drops to buy, or whether the ones you have are right.
  • Your baby was born early, or has a medical condition, as they may need something different.
  • You think you may be entitled to Healthy Start and want help applying.
  • You are worried about your own vitamin D levels, particularly if you were deficient in pregnancy.

Call 999 or take your baby straight to A&E if your baby:

  • Is floppy or unresponsive
  • Will not wake for feeds
  • Is having trouble breathing, or their lips, tongue or gums look blue or grey
  • Has a sunken fontanelle
  • Is visibly jaundiced and unwell with it, for example floppy, hard to wake or not feeding. Yellowing shows most clearly in the whites of the eyes, the gums, and the palms and soles
  • Has dark urine or pale, chalky stools

How a consultation helps

Vitamin D is not usually the reason anyone books me, but it comes up in almost every visit, because it is the sort of practical thing that gets lost between the midwife discharging you and the health visitor arriving. When I visit, we go through the everyday admin of feeding alongside the feeding itself, so you leave knowing what your baby actually needs rather than wondering whether you have missed something.