01OverviewDefinition, clinical context and the essential points that orientate the chapter.
After cord clamping, placental glucose stops abruptly. Glycogenolysis, gluconeogenesis, lipolysis and ketogenesis must maintain brain fuel while feeding becomes established. A brief fall is physiological, but severe, symptomatic or persistent low glucose is not.
No single concentration perfectly predicts brain injury. UK practice therefore uses operational thresholds that trigger action based on concentration, clinical signs, persistence and risk rather than defining one universal biochemical disease boundary.
Infants of mothers with diabetes may have fetal hyperinsulinaemia after exposure to high maternal glucose; after birth insulin persists while glucose supply falls. Similar hyperinsulinism can follow perinatal stress and growth restriction.
Small or growth-restricted infants have limited glycogen and fat, while large infants can be hyperinsulinaemic. Preterm and ill babies also have immature counter-regulation and require neonatal-unit protocols beyond the healthy term framework.
Symptoms include jitteriness, poor feeding, hypothermia, abnormal cry, lethargy, hypotonia, apnoea, cyanosis and seizures. None is specific; infection, hypoxic injury, electrolyte disorders and drug exposure must be considered.
Dextrose gel raises glucose while preserving mother-baby contact and feeding in well babies. It is applied to buccal mucosa and followed immediately by an effective feed; swallowing it without mucosal massage reduces its intended delivery.
Intravenous treatment is required when the baby is unwell, neurological, severely low or unable to maintain glucose with feeding and gel. Increasing glucose delivery should be calculated in mg/kg/min rather than by arbitrary fluid changes.
Persistent hyperinsulinaemic hypoglycaemia suppresses ketones and free fatty acids, depriving the brain of alternative fuel. A sample obtained during hypoglycaemia is far more diagnostic than tests after glucose normalises.
Prevention is active: warmth, early uninterrupted skin-to-skin contact, prompt effective feeding, skilled lactation support and avoidance of unnecessary separation reduce risk without ignoring babies who need treatment.
Key points
- Screen only babies with recognised risk or abnormal signs; routine testing of healthy term babies without risk can disrupt feeding and cause unnecessary treatment.
- Risk includes maternal diabetes, beta-blocker exposure, fetal growth restriction, birth weight below the 2nd centile, macrosomia, hypothermia and significant perinatal illness.
- Feed an at-risk well baby within the first hour, support skin-to-skin contact and check blood glucose before the second feed at 2–4 hours of age.
- Use a ward glucose analyser or blood-gas analyser at low ranges. Bedside meters may screen, but confirm unexpectedly low or persistent values without delaying treatment.
- BAPM operational thresholds for term infants in the first 72 hours are below 1.0 mmol/L at any time, below 2.5 mmol/L with abnormal signs, or persistent below 2.0 mmol/L on repeat in an at-risk well baby.
- First-line for a well, feeding term infant with glucose 1.0–1.9 mmol/L is feeding support plus 40% dextrose gel 200 mg/kg, equivalent to 0.5 mL/kg, massaged into the buccal mucosa.
- Recheck glucose about 30 minutes after gel and feeding. Repeat and escalate according to the BAPM/local pathway; repeated gel must not postpone neonatal assessment.
- For neurological signs or glucose below 1.0 mmol/L, give urgent IV 10% glucose and start a controlled infusion; obtain a critical sample first only if immediately available.
- Do not use undiluted concentrated glucose through peripheral veins. Calculate the glucose infusion rate, prescribe pump rate clearly and use independent neonatal dose checks.
- Investigate sepsis, hypothermia, hypoxia and feeding failure concurrently. A corrected glucose does not explain why it fell.
- Take a critical sample during recurrent severe hypoglycaemia for laboratory glucose, insulin, C-peptide, ketones, free fatty acids, cortisol, growth hormone and metabolic tests guided by specialists.
- Before discharge confirm stable pre-feed glucose through several feed-fast cycles, an effective feeding plan, resolved cause or specialist plan and clear parental safety-netting.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Limited substrate
Prematurity, growth restriction, poor intake and hypothermia exhaust small glycogen and fat stores and reduce glucose production.
Excess insulin
Maternal diabetes, perinatal stress and congenital hyperinsulinism maintain peripheral glucose uptake while suppressing protective ketone production in the newborn.
Increased consumption
Sepsis, hypoxia, respiratory work and cold stress increase whole-body metabolic demand beyond available glucose production and enteral intake.
Endocrine or metabolic disease
Cortisol or growth-hormone deficiency, glycogen disorders, gluconeogenic defects and fatty-acid oxidation disorders cause recurrent or persistent neonatal hypoglycaemia.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Interrupted placental supply
Cord clamping ends continuous maternal glucose transfer and demands rapid neonatal glycogenolysis, gluconeogenesis and alternative-fuel generation after birth.
- 2Neuroglycopenia
Insufficient glucose and alternative fuel disrupt neuronal energy, producing altered feeding, tone, consciousness, breathing or seizures.
- 3Hyperinsulinaemic fuel blockade
Inappropriate circulating insulin both lowers glucose and suppresses lipolysis and ketogenesis, thereby increasing neonatal brain vulnerability to fuel failure.
- 4Recurrent injury
Severity, duration, repetition and underlying illness combine to determine neurological risk rather than one value alone.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Before birth identify maternal diabetes, medicines including beta blockers, growth restriction, large size, prematurity, perinatal stress and known metabolic or endocrine risk.
After birth assess temperature, alertness, tone, suck, respiratory pattern, colour, perfusion and feeding; jitteriness that stops when a limb is held differs from clonic seizure activity but still warrants assessment.
Measure glucose immediately for abnormal signs. In an asymptomatic at-risk term baby, feed within 1 hour and measure before the second feed at 2–4 hours.
Document sampling method, device, time relative to feed or gel, exact value, symptoms, temperature and action; an isolated number without context is unsafe.
Assess milk transfer, feeding frequency, urine, weight and hydration rather than assuming the prescribed feed occurred effectively.
Recognise persistence through repeated low pre-feed values, rising IV glucose requirement or recurrence after 48–72 hours, and involve metabolic or endocrine specialists early.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
First-line: accurate blood glucose measurementFirst stepFirst line - Why
- Confirm hypoglycaemia and guide time-critical treatment.
- Interpretation and limitations
- Low-range accuracy matters. Use a ward or blood-gas analyser when possible and send laboratory confirmation for persistent or unexpected results, but never delay treatment of a symptomatic or profoundly low baby.
- 02
Clinical and feeding assessment - Why
- Identify signs, ineffective intake, hypothermia and concurrent illness.
- Interpretation and limitations
- A well feeding baby and a lethargic baby with the same number require different urgency; abnormal signs lower the operational action threshold.
- 03
Critical hypoglycaemia sample - Why
- Distinguish hyperinsulinism, cortisol or growth-hormone deficiency, fatty-acid oxidation disorder and other metabolic disease.
- Interpretation and limitations
- Obtain during a genuine low glucose before treatment only when this causes no delay; suppressed ketones and free fatty acids with detectable insulin supports inappropriate insulin action.
- 04
Sepsis and organ-function tests - Why
- Assess infection, hypoxia, liver disease, renal dysfunction and electrolyte disturbance in an unwell infant.
- Interpretation and limitations
- Blood culture, gas, lactate, FBC, CRP, electrolytes and liver tests are selected by presentation; normal glucose after treatment does not exclude sepsis.
- 05
Endocrine and metabolic confirmation - Why
- Define persistent disease after critical results or high glucose requirement.
- Interpretation and limitations
- Specialists may request acylcarnitines, amino and organic acids, ammonia, cortisol testing, genetics and controlled fasting; unsupervised fasting in a neonate is unsafe.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Sepsis or hypoxic illness
Both consume glucose and cause lethargy, temperature change, apnoea and poor feeding, requiring concurrent urgent clinical assessment.
Normal neonatal movements
Jitteriness may be stimulus-sensitive and cease with restraint, unlike seizures, but glucose and clinical state still need checking.
Electrolyte or neurological disorder
Hypocalcaemia, intracranial injury and maternal drug withdrawal can mimic hypoglycaemic tremor, irritability, altered tone or neonatal seizures.
Persistent metabolic-endocrine disease
Recurrent low glucose, hepatomegaly or high intravenous glucose requirement shifts assessment beyond normal transitional neonatal metabolic adaptation.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01RiskPrevent and screenFirst stepA term baby is well but has a recognised hypoglycaemia risk.+
- 1Keep warm and in skin-to-skin contact and feed within 1 hour.
- 2Measure glucose before the second feed at 2–4 hours and assess feeding directly.
- 3Continue pre-feed monitoring and feeding support until the BAPM discharge criteria are met.
02Well babyFeeding and gelGlucose is 1.0–1.9 mmol/L without abnormal clinical signs.+
- 1Give 40% dextrose gel 0.5 mL/kg to buccal mucosa and feed effectively.
- 2Recheck glucose after about 30 minutes and repeat only within the current pathway limits.
- 3EscalationEscalate persistent values below 2.0 mmol/L, feeding failure or any new clinical sign to neonatal care.
03EmergencyIntravenous glucoseGlucose is below 1.0 mmol/L or abnormal neurological or clinical signs are present.+
- 1Stabilise ABC and temperature, call senior neonatal help and obtain IV access.
- 2Give 10% glucose 2.5 mL/kg over 5 minutes and commence 10% glucose 60 mL/kg/day under the term BAPM pathway.
- 3Recheck after 30 minutes, calculate infusion rate and titrate while investigating the cause; use gel only as a bridge if access is delayed.
04PersistentFind the mechanismLow values recur, require high glucose delivery or persist beyond expected transition.+
- 1Obtain critical samples during hypoglycaemia and review medicines, growth, liver size and perinatal stress.
- 2Involve neonatal endocrine or metabolic specialists and avoid unsupervised fasting.
- 3Use cause-specific therapy and establish a safe feed-fast plan before discharge.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Dextrose 40% oral gel
200 mg/kg, equivalent to 0.5 mL/kg, massaged into the buccal mucosa and followed immediately by an effective feed. Repeat only within the current BAPM and local pathway after reassessment.Not definitive treatment for neurological signs, severe illness or glucose below 1.0 mmol/L. Check concentration and dose by current weight, avoid simply squirting it into the throat, document cumulative doses and do not let repeated gel delay IV treatment.
Glucose 10% intravenous
Under the BAPM term pathway for glucose below 1.0 mmol/L or abnormal signs, give 2.5 mL/kg IV over 5 minutes, then start 60 mL/kg/day by infusion and recheck glucose after 30 minutes. Titrate glucose infusion rate through the neonatal protocol.Use neonatal pump and independent dose checks. Obtain critical samples first only if treatment is not delayed. Monitor line site, fluids, sodium and glucose closely; higher concentrations usually require central access and specialist prescribing.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Brain injury
Severe, prolonged or recurrent neonatal neuroglycopenia can impair vision, motor function, cognition, development and later seizure control.
Feeding disruption
Unnecessary parent-infant separation and supplementation may impair breastfeeding, while untreated ineffective intake perpetuates low neonatal blood glucose.
IV treatment harm
Extravasation, fluid overload, electrolyte disturbance and rebound hypoglycaemia can arise from poorly calculated or monitored intravenous infusion changes.
Missed persistent disease
Failure to sample recurrent hypoglycaemia during the low value can delay treatment of hyperinsulinism, adrenal insufficiency or serious metabolic disease.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Recheck glucose approximately 30 minutes after gel, feed or IV bolus and after each material change in glucose delivery.
- Continue pre-feed measurements until values are stable through repeated feed-fast cycles under the current BAPM or neonatal-unit pathway.
- Trend temperature, feeding effectiveness, urine, weight, neurological state and cardiorespiratory observations with the glucose values.
- For IV therapy calculate and document glucose infusion rate in mg/kg/min and reassess fluid, sodium and line safety at every increase.
- Monitor peripheral sites closely because concentrated glucose extravasation injures tissue; use central access for concentrations above the local peripheral limit.
- Persistent disease needs ketone monitoring, response to therapy, specialist investigations and a written emergency plan.
- After symptomatic or severe hypoglycaemia arrange neurodevelopmental surveillance proportionate to duration, cause and neurological findings.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Operational threshold
The BAPM values are action points integrating symptoms and persistence, not proof that every lower value causes injury or every higher value is safe.
Gel follows mucosal technique
Measure 0.5 mL/kg of 40% gel, dry the buccal mucosa if necessary, massage it in and provide an effective feed immediately.
Think in glucose delivery
Ten percent glucose at 60 mL/kg/day supplies about 4.2 mg/kg/min; rate and concentration together determine metabolic treatment.
Critical means during low glucose
Insulin, ketones and counter-regulatory hormones after correction cannot reliably reconstruct the mechanism present during hypoglycaemia.
Term framework has boundaries
Very preterm and sick infants need neonatal-unit pathways because fluid, nutrition and treatment thresholds interact differently from well term adaptation.
11Common pitfallsFrequent interpretation and management errors.
- 01
Do not screen a healthy term baby without risk solely because testing is available.
- 02
Do not dismiss jitteriness or poor feeding without measuring glucose and assessing the infant.
- 03
Do not treat a meter's low-range result as perfectly accurate, but do not wait for laboratory confirmation in an emergency.
- 04
Do not use gel alone for seizures, altered consciousness or glucose below 1.0 mmol/L.
- 05
Do not repeat gel indefinitely while glucose remains below 2.0 mmol/L.
- 06
Do not increase fluid without calculating glucose infusion rate, sodium delivery and total fluid consequences.
- 07
Do not obtain a critical sample if doing so will delay urgent glucose treatment.
- 08
Do not discharge until feeding and pre-feed glucose are stable and persistent disease has been excluded or safely managed.