Low Blood Sugar (Hypoglycaemia) in Newborns
Which babies are monitored for low blood sugar in the first days, why frequent feeds help, and what treatment looks like.
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- 6 sources
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- Dr Jubal John, FRACP
- Category
- medical guides
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Take-home
Most healthy term babies regulate their blood sugar well in the first hours of life. A defined group of babies, those with recognised risk factors such as late preterm birth, growth restriction, large size, or maternal diabetes, are monitored with heel-prick glucose tests in the first 24–48 hours because they are more likely to dip. When low sugars are found, the usual first steps are feed early, feed often, keep baby warm, and re-check. Most transient low sugars correct quickly with feeding alone; persistent or severe hypoglycaemia needs closer assessment and treatment.
What is neonatal hypoglycaemia?
Hypoglycaemia means low blood sugar (glucose). Glucose is your baby’s main energy source, especially for the brain.
The normal transition after birth
Before birth, your baby received a steady supply of glucose through the placenta. After birth, they have to regulate their own blood sugar by:
- Breaking down stored glycogen from the liver
- Taking in glucose from milk feeds
- Making new glucose in the liver (gluconeogenesis)
Most term, healthy babies do this smoothly. A defined group need a helping hand.
In neonatal practice we aim to keep blood glucose above 2.6 mmol/L in the first 48 hours. Below that, a plan is made, usually more feeding and a recheck.
Which babies are monitored?
Many babies born in Australia fall into one of the recognised risk groups and have routine blood-sugar checks in the first 12–24 hours. Being in a monitoring group does not mean your baby will have low sugar, most don’t. It means a test is done to be sure.
Green — usually fine
Baby-side risk factors
- Small for gestational age (SGA): birth weight under the 10th centile (about 1 in 10 babies, by definition of the centile cut-off)
- Large for gestational age (LGA): birth weight over the 90th centile (about 1 in 10 babies, by definition of the centile cut-off)
- Late preterm: born between 35 and 36+6 weeks. Pre-term births account for around 8% of all births; late preterm makes up most of that group.
- Low birth weight: under 2.5 kg at term
- Birth asphyxia or difficult resuscitation at birth
- Cold stress or difficulty maintaining temperature
- Polycythaemia (thick blood) or significant jaundice
Amber — be alert
Mother-side risk factors
- Diabetes in pregnancy: gestational, type 1, or type 2. Around 1 in 5 pregnancies in Australia are affected by gestational diabetes (AIHW, 2021–22).
- Certain medications: beta-blockers (e.g. labetalol), oral hypoglycaemics, intravenous glucose in labour
- Pre-eclampsia or growth restriction
Red — act now
Other situations that prompt testing
- A baby who isn’t feeding well in the first 6–8 hours
- Any baby with symptoms (see below)
Most at-risk babies do not develop hypoglycaemia
Being in a monitoring group is a safety-net, not a diagnosis. In well-controlled gestational diabetes, most babies test normally and follow the standard postnatal plan, the monitoring is to catch the smaller number who need feeding adjustment or dextrose gel.
Signs to watch for
Many babies with low blood sugar show no obvious signs
This is precisely why babies in monitoring groups are tested routinely rather than waited on for symptoms. When signs do appear, they may include:
Green — usually fine
Mild signs
- Jitteriness or tremors (that don’t stop when you hold the limb still)
- Poor feeding or a weak suck
- Unusual sleepiness
Amber — be alert
Moderate signs
- Irritability or high-pitched cry
- Low body temperature despite normal wrapping
- Floppiness or poor muscle tone
Red — act now
Severe signs: tell staff / call 000 straight away
- Breathing difficulties or apnoea (pauses in breathing)
- Seizure or unusual jerking movements
- Unresponsive, blue, or very pale
How we monitor blood sugar
Testing in hospital
The test is a heel-prick: a quick spring-loaded lance on the side of the baby’s heel, a tiny drop of blood, and a result on the ward meter within seconds.
When tests are typically done
- Before the second feed (around 2–3 hours of age): the expected lowest point in the transition
- Before feeds for the next 12–24 hours, depending on the risk group and early results
- Extra tests if the baby is unsettled, sleepy, cold, or feeding poorly
- Testing stops once three consecutive pre-feed sugars are above 2.6 mmol/L and the baby is feeding well
Target levels
The goal is blood glucose above 2.6 mmol/L in the first 48 hours, rising to above 3.0 mmol/L from 48 hours onward. A single reading slightly below 2.6 in a well-feeding baby is not a disaster, it triggers a feed and a re-check.
What happens if a test comes back low
Most low sugars respond rapidly to the simplest treatment: a feed. The usual step-up looks like this:
- Feed the baby: breast, or breast + top-up of colostrum, expressed milk or formula
- Recheck in 30 minutes: sugars should rise with feeding
- If still low: a second top-up, sometimes a 40% glucose gel rubbed onto the inside of the cheek, this is a routine, safe buccal treatment used widely across Victorian postnatal wards
- If still low despite these steps, or the baby is unwell: an IV glucose infusion in the nursery or NICU for a short period, usually 24–48 hours, while feeds continue
Moving up the ladder is not a failure, it is what the monitoring is for. Most babies stay on steps 1–3.
Prevention: the feeding-first approach
What actually helps
- First feed within 60 minutes of birth where possible, colostrum is highly concentrated and helps stabilise glucose
- Skin-to-skin contact from birth, keeps baby warm, calmer, and cues feeding behaviours
- Feed every 2–3 hours in the first 48 hours, do not let a monitored baby go longer than 3 hours without a feed
- Keep baby warm and dry: cold babies burn through glucose fast
- Colostrum harvesting antenatally (from around 36 weeks, for women with gestational diabetes): stored colostrum can be a ready top-up if needed. Discuss this with your midwifery team.
- Tell your midwife if your baby isn’t feeding well, looks different, or you have any concern
What you can do
During your hospital stay
- Feed frequently, aim for 8–12 feeds per 24 hours
- Wake your baby for feeds if they’re not self-waking (3-hourly in monitoring groups)
- Skin-to-skin contact as much as you can, it has a measurable effect on sugar stability
- Tell staff straight away if baby seems unwell, too sleepy, or won’t latch
- Ask about every test result, you’re entitled to know what the number was and what the plan is
After going home
Once monitoring has ended and the baby is feeding well, the risk of recurrence is very low. At home, watch for the same markers of good feeding as any baby:
- 4–6+ heavy wet nappies per 24 hours from day 5 onwards (fewer in the first few days, building up as feeding establishes)
- 3 or more mustard-yellow stools per day in the first 6 weeks (breastfed babies)
- Baby alert between feeds, rousable, and reasonably settled
- Regained birth weight by 10–14 days
Contact us, your GP, or the MCH nurse if any of these slip.
Long-term outlook
The good news
- Most babies with transient hypoglycaemia stabilise within 48–72 hours
- Once feeding is established, the problem typically does not recur
- No special diet or monitoring is needed after discharge in the vast majority
- Normal growth and development are expected
Persistent or recurrent hypoglycaemia (for example, from an underlying endocrine or metabolic condition such as congenital hyperinsulinism) is rare, and is worked up separately by paediatric endocrinology if the usual feeding approach doesn’t stabilise sugars by 72 hours, in line with the Safer Care Victoria neonatal eHandbook.
When to seek help
In hospital
Tell your midwife or nurse immediately if your baby looks different, is hard to wake, jittery, cold, or not feeding. They can reach our on-call specialist 24/7.
Green — usually fine
Green: expected
- Feeding 8–12 times in 24 hours
- Alert between feeds, rousable for each feed
- Stable temperature with normal wrapping
- Glucose levels stable and monitoring has finished
Amber — be alert
Amber: tell staff / ring us
- Feeding less well than earlier in the day
- Sleepier than usual but still rousable
- Jittery movements that settle when you hold the limb still
- Cold hands and feet with a cool chest or tummy
Red — act now
Red: tell staff now / call 000 at home
- Will not wake for feeds, or extremely sleepy / floppy
- Seizures or unusual jerking movements that don’t stop when a limb is held still
- Breathing difficulties, apnoea (pauses ≥20 seconds or any pause with colour change), or colour change
- Feels cold and won’t warm up despite extra wrap and skin-to-skin
- High-pitched, painful-sounding cry
Common questions
“Will my baby need a NICU admission?”
Most monitored babies stay on the postnatal ward with mum. A short NICU or Special Care Nursery stay (24–48 hours, usually for IV glucose) is needed in only a small proportion, and even then, babies typically go home with no ongoing treatment.
“Can low blood sugar cause brain damage?”
Severe, untreated, prolonged hypoglycaemia can affect the brain, which is exactly why monitoring exists. The thresholds, tests, and treatment ladder used in hospitals here are there to catch and treat low sugars promptly. Isolated dips that are quickly corrected have no measurable long-term effect.
“My baby had glucose gel: is that dangerous?”
No. 40% dextrose buccal gel is a safe, evidence-based first-line treatment. The Sugar Babies RCT (Lancet 2013) showed dextrose gel reduced treatment failure compared to placebo when used to treat hypoglycaemia, and the larger hPOD multicentre trial (PLOS Medicine 2021) extended the evidence base to prevention in at-risk babies.
“My baby is breastfed: will that be enough?”
Usually yes. Colostrum is dense in energy and well-suited to the first days. In monitoring groups, small top-ups (expressed colostrum or formula) are sometimes added in the first 24–48 hours if a sugar is low, they’re a short-term bridge, not a sign that breastfeeding has failed.
“Will this happen again?”
Transient neonatal hypoglycaemia almost never recurs once feeding is established. If your baby had it, the next sibling may be slightly more likely to be monitored (often because the same risk factors apply), but again, monitoring, not a foregone conclusion.
Related reading
Worried about your baby's feeding or sugars?
If you're in our care at Frances Perry, tell your midwife and the paediatric team will be contacted. At home, poor feeding or sugar concerns warrant a same-day feeding and weight review with your GP or MCH nurse.