BACKGROUND: Neonatal hypoglycaemia is a common condition that can be associated with brain injury. Current practice usually includes early identification of at-risk infants (e.g. infants of diabetic mothers; preterm, small- or large-for-gestational-age infants), and prophylactic measures are advised. However, these measures often involve use of formula milk or admission to the neonatal unit. Dextrose gel is non-invasive, inexpensive and effective for treatment of neonatal hypoglycaemia. Prophylactic dextrose gel can reduce the incidence of neonatal hypoglycaemia, thus potentially reducing separation of mother and baby and supporting breastfeeding, as well as preventing brain injury. This is an update of a previous Cochrane Review published in 2021. OBJECTIVES: To assess the effectiveness and safety of oral dextrose gel in preventing hypoglycaemia before first hospital discharge and reducing long-term neurodevelopmental impairment in newborn infants at risk of hypoglycaemia. SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase and Epistemonikos in April 2023. We also searched clinical trials databases and the reference lists of retrieved articles. SELECTION CRITERIA: We included randomised controlled trials (RCTs) and quasi-RCTs comparing oral dextrose gel versus placebo, no intervention, or other therapies for the prevention of neonatal hypoglycaemia. We included newborn infants at risk of hypoglycaemia, including infants of mothers with diabetes (all types), high or low birthweight, and born preterm (< 37 weeks), age from birth to 24 hours, who had not yet been diagnosed with hypoglycaemia. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed the risk of bias. We contacted investigators to obtain additional information. We used fixed-effect meta-analyses. We used the GRADE approach to assess the certainty of evidence. MAIN RESULTS: We included two studies conducted in high-income countries comparing oral dextrose gel versus placebo in 2548 infants at risk of neonatal hypoglycaemia. Both of these studies were included in the previous version of this review, but new follow-up data were available for both. We judged these two studies to be at low risk of bias in 13/14 domains, and that the evidence for most outcomes was of moderate certainty. Meta-analysis of the two studies showed that oral dextrose gel reduces the risk of hypoglycaemia (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.79 to 0.95; risk difference (RD) -0.06, 95% CI -0.10 to -0.02; 2548 infants; high-certainty evidence). Evidence from two studies showed that there may be little to no difference in the risk of major neurological disability at two years of age after oral dextrose gel (RR 1.00, 95% CI 0.59 to 1.68; 1554 children; low-certainty evidence). Meta-analysis of the two studies showed that oral dextrose gel probably reduces the risk of receipt of treatment for hypoglycaemia during initial hospital stay (RR 0.89, 95% CI 0.79 to 1.00; 2548 infants; moderate-certainty evidence) but probably makes little or no difference to the risk of receipt of intravenous treatment for hypoglycaemia (RR 1.01, 0.68 to 1.49; 2548 infants; moderate-certainty evidence). Oral dextrose gel may have little or no effect on the risk of separation from the mother for treatment of hypoglycaemia (RR 1.12, 95% CI 0.81 to 1.55; two studies, 2548 infants; low-certainty evidence). There is probably little or no difference in the risk of adverse effects in infants who receive oral dextrose gel compared to placebo gel (RR 1.22, 95% CI 0.64 to 2.33; two studies, 2510 infants; moderate-certainty evidence), but there are no studies comparing oral dextrose with other comparators such as no intervention or other therapies. No data were available on exclusive breastfeeding after discharge. AUTHORS' CONCLUSIONS: Prophylactic oral dextrose gel reduces the risk of neonatal hypoglycaemia in at-risk infants and probably reduces the risk of treatment for hypoglycaemia without adverse effects. It may make little to no difference to the risk of major neurological disability at two years, but the confidence intervals include the possibility of substantial benefit or harm. Evidence at six to seven years is limited to a single small study. In view of its limited short-term benefits, prophylactic oral dextrose gel should not be incorporated into routine practice until additional information is available about the balance of risks and harms for later neurological disability. Additional large follow-up studies at two years of age or older are required. Future research should also be undertaken in other high-income countries, low- and middle-income countries, preterm infants, using other dextrose gel preparations, and using comparators other than placebo gel. There are three studies awaiting classification and one ongoing study which may alter the conclusions of the review when published.