My mother-in-law gave my 2-week-old some

Finish the call to the pediatrician today — that call is the right door for this, and a sip of plain water is not a poisoning emergency you need to chase tonight. But your baby is two weeks old, so you are also right to want it looked at rather than assumed.

Is the water itself dangerous?

Not needed, and not the same as dangerous. The World Health Organization's breastfeeding page (page dated 2 October 2024, checked 14 October 2026) says: "Breastfeeding alone can provide all the food and water your baby needs for the first six months of their lives. Babies do not need any food or drink except breast milk, not even water, until they are six months old."

So plain water at two weeks old is a sip your baby did not need. What matters more is two other things: what was in it besides water, and whether your baby has fed and wet nappies as usual since.

I can't tell you how much water is a problem for your baby, and I don't diagnose — that is the pediatrician's call, and it's the one thing the call is for.

1. What you've tried, and the better version of it

Tried: assuming a small sip is always harmless. That quietly keeps two useful things off the table — the amount, and whether there was anything else in the cup.

Better: make the two-minute call you are already on hold for, and hand them five facts.

1. Baby's age: 2 weeks.
2. Roughly when the water was given.
3. Roughly how much — "a spoonful", "a couple of mouthfuls", "a full small cup", "I don't know, it happened fast". "I don't know" is a perfectly good answer.
4. What was in it: plain tap water, or something with sugar, honey, herbs, rice water, or a medicine in it.
5. Whether the baby has fed and wet nappies normally since, and whether they coughed or spluttered at the time.

That's the whole ask. You do not need to arrive with a conclusion — "my mother-in-law gave the baby water, I don't know how much, please tell me what to watch for" is a complete and sufficient thing to say to a pediatrician.

On the family part: tonight's job is the baby, not the verdict. One line, said once, is enough: "She needs milk, not water — let's ask the doctor together and follow what they say." Most grandparents hear that as being on the team. Save the longer conversation for after the visit, when you're not holding a newborn.

2. Avoid list — from tonight onward

• No more water, herbal tea, rice water, "gripe water", or anything else given by mouth until the pediatrician says otherwise. If it was honey or sugar mixed in, say that explicitly on the call — a clinician needs to know that specific fact.
• Do not change the formula strength to "make up for it." Make formula exactly as the tin or sachet says. Diluted formula is its own problem in a baby this age.
• Do not try to flush it out — no vomiting, no charcoal, no salt water, no leftover medicine from anyone else's box.
• Don't start, stop, or change any medicine or supplement because of this.
• Don't skip or delay the next normal feed waiting to "clear it out."
• Don't cancel the call because the baby looks fine. The reason to call is that nobody knows the amount, and two weeks old is exactly when you ask instead of guess.

3. Tonight and today — a short list

1. Finish the pediatrician call, with the five facts above.
2. Go back to your baby's usual rhythm: feed when the baby asks, as normal.
3. Count wet nappies from now, and note the times. Ask the pediatrician what number is your baby's normal, and what to do if it's below that.
4. Write down the time of the water and whether there was any cough, splutter, or choking at the time.
5. Keep the baby warm and hold them — skin to skin if that's your usual way.

Decision tree

Call your local emergency number now if you see: hard or fast working to breathe, grunting or sucking in between the ribs, blue or grey colour around the lips or face, pauses in breathing, a fit, or the baby is floppy, won't wake properly, or has a weak cry.

Go to the pediatrician or urgent care today, do not wait for morning, if you see: feeding poorly or noticeably less often than usual, unusually sleepy or hard to rouse, fewer wet nappies than the baby normally has, any vomiting (green or bile-looking especially), a temperature that feels hot or cold, or simply that the baby "isn't right" and you can't say why. In a two-week-old, not right is enough of a reason.

Stay on the plan above if: they coughed or spluttered once and then settled, they've fed normally since, they're producing their usual wet nappies, they're awake and settled between feeds. You still make the call today — this just tells you where tonight sits.

What 24 hours looks like

Not a cure — a checklist. By tonight or tomorrow morning you should have: the call done; feeds and nappies back on your baby's own pattern; an answer from the pediatrician about anything that was in that cup; and the disagreement about water parked until after the visit. If a red flag shows up in the meantime and you act on it, the plan worked — that's what going is for.

The one thing I'd still like to know: was it plain tap water or something with sugar, honey or herbs in it, roughly how much, and did the baby cough or splutter? That one answer changes what happens tonight. Everything else can wait for the pediatrician.

Sources: the World Health Organization breastfeeding page above (checked 14 October 2026), and the Royal Children's Hospital Melbourne paediatric emergency guidance, which is where the red-flag list comes from. Where a baby is unwell at under three months, RCH treats it as needing assessment rather than home observation.