Baby vomiting: when it is normal, when it needs a doctor
Almost every baby vomits at some point. A lot of it is entirely harmless and goes with the territory of a small, developing digestive system. But some patterns of vomiting do need attention, and knowing which is which can save you a lot of worry. This guide explains the differences, helps you spot the signs of dehydration early, and tells you clearly when to call for help.
Vomiting vs posseting vs reflux: the differences
Posseting is the small amount of milk that flows back up after a feed, often arriving with a burp. It is very common, usually effortless for your baby, and does not cause distress. Many babies posset after most feeds throughout the first year and are otherwise perfectly well. If your baby is gaining weight, feeding contentedly and not seeming bothered, posseting is almost always nothing to worry about.
Reflux (gastro-oesophageal reflux, or GOR) is more frequent and involves larger volumes coming back up. Some babies experience discomfort with it, crying during or after feeds, arching their back or seeming unsettled. Most babies grow through reflux as their digestive system matures, usually by the time they are sitting up reliably.
Vomiting is forceful and larger in volume. It often has a cause worth investigating, whether that is a viral illness, overfeeding, or in rarer cases a structural issue. Understanding which of the three you are dealing with helps you tell the doctor the right story when you call.
Common causes of vomiting in babies
The most common cause of true vomiting in babies is a viral illness, particularly gastroenteritis. Other causes include:
- Feeding too quickly or overfeeding, especially with bottle feeding, where the flow can be faster than your baby can comfortably manage
- Motion sickness, which can affect babies from around six months as the vestibular system develops
- Worsening reflux during illness, teething, or a growth phase
- Pyloric stenosis, a narrowing of the outlet between the stomach and small intestine; this is uncommon but important to know about because it causes forceful, projectile vomiting at every feed from around two to eight weeks of age, and leads to poor weight gain; it needs prompt treatment
Caring for a vomiting baby
If your baby is vomiting but is alert, producing wet nappies and keeping some feeds down, you can manage things at home while keeping a close eye on them.
- Offer smaller, more frequent feeds rather than large volumes in one go
- If you are breastfeeding, continue to feed on demand; breastmilk is the best fluid and provides antibodies to help your baby recover
- Formula-fed babies can be offered smaller amounts more often than usual
- For babies over six months who are vomiting, small sips of water between feeds are fine
- Keep your baby upright for around 30 minutes after feeds to let gravity help
- Do not give anti-nausea medicines unless your doctor or nurse prescribes them
Recognising dehydration
Dehydration is the main risk when a baby is vomiting, and it can develop more quickly in young babies than you might expect. Watch for these signs and contact your GP or 111 the same day if you see them:
- Fewer wet nappies than usual (fewer than six in 24 hours for a young baby is a concern)
- A sunken soft spot (fontanelle) on the top of your baby's head
- Dry mouth and lips
- No tears when crying
- Very dark yellow urine
- Unusual lethargy or limpness
If you are keeping track of wet nappies, you will notice early if things are changing. That early warning is worth a lot.
Red flag vomiting patterns that need urgent assessment
Some patterns of vomiting need to be seen quickly. Seek urgent help for any of the following:
- Vomit that contains blood, whether bright red or dark brown (like coffee grounds)
- Green or bile-coloured vomit at any age (this can indicate a bowel obstruction and needs immediate assessment)
- Projectile vomiting in a baby under two months at every single feed (possible pyloric stenosis)
- Vomiting after a head injury
- Vomiting that is not improving after 12 to 24 hours in a baby under three months
- Vomiting combined with a high fever, severe abdominal pain, a rash, or unusual drowsiness at any age
When to call 111 vs 999
Call 999 or go to A&E immediately if your baby is unresponsive, has green vomit with a visibly swollen or hard belly, or is showing signs of severe dehydration such as extreme limpness, no response to you, or very sunken eyes and fontanelle.
Call 111 if vomiting is persistent and you are unsure what to do, if you are concerned about dehydration, if your baby is under three months and has vomited more than twice, or if you simply want guidance. When in doubt, calling 111 is always the right move. A clinician will help you decide the next step.
Oral rehydration solution for babies
In babies under one year, oral rehydration solutions (ORS) such as Dioralyte are not routinely recommended unless your doctor or 111 specifically advises it. Breastmilk or formula is the right fluid for most babies during a vomiting illness, as it provides not just fluid but calories and the immune support they need. ORS may be recommended in specific situations, particularly for older babies with significant fluid loss. If a clinician advises it, follow their guidance on how much to give and when.
Frequently asked questions
How is vomiting different from reflux or spit-up?
Spit-up (posseting) is small, effortless and happens shortly after feeds. Reflux is more frequent and may cause some discomfort. Vomiting is forceful, larger in volume and is often associated with illness. If your baby is gaining weight and not distressed, small spit-ups are usually normal and not a cause for concern.
Should I give my baby water when they are vomiting?
For babies under six months, continue breastmilk or formula as normal and do not substitute water. For babies over six months, small sips of water between feeds are fine, but milk should remain the main fluid. Babies need the calories and nutrients in milk, especially during illness.
What is oral rehydration solution and do I need it?
Oral rehydration solution (such as Dioralyte) replaces the salts and sugars lost during vomiting and diarrhoea. In babies under one year, it is generally only given on medical advice, as breastmilk or formula is usually sufficient for mild illness. If a clinician advises ORS, use it exactly as directed on the packet and in the right amount for your baby's weight.
When should I worry about a baby vomiting?
Contact your GP or 111 if vomiting lasts more than 24 hours, if you see any signs of dehydration, if there is blood or green colour in the vomit, or if your baby is under three months and vomiting repeatedly. Always call if something feels wrong, even if you cannot put your finger on exactly what.
Can babies get travel sickness?
Yes, though it is more common from around six months, once the vestibular system that controls balance has matured a little more. Signs include restlessness and unsettled behaviour in the car before vomiting. Short journeys, good ventilation, and keeping your baby facing forward in an age-appropriate car seat can all help.
Is green vomit always serious?
Green or bile-coloured vomit is a red flag in babies and should always be assessed urgently. It can indicate a bowel obstruction, which needs immediate treatment. Do not wait and see if your baby's vomit is green. Call 999 or go to A&E.
Log feeds and nappies through every sick day
Cubby makes it simple to keep track of what is going in and what is coming out, so you can spot dehydration early and have the information your doctor needs.
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