Inclusion Criteria:  Children with functional constipation diagnosed based on Rome IV criteria  Exclusion Criteria:  Children with organic causes of constipation; eg, anorectal malformations, or Hirschsprung's disease Children who fulfil the criteria of Irritable Bowel Syndrome Significant, unstabilised chronic health conditions requiring major drug adjustment during the last 3 months. Unintentional weight loss greater than or equal to 5% of their body weight within the last 3 months Recurrent or unexplained fevers History of abdominal surgery involving the luminal gastrointestinal tract, except appendectomy, or hernia repairs Concomitant use of drugs that are known to affect gastrointestinal motility Established diagnoses of autism spectrum disorders Mental retardation Children who are exclusively breastfed Non-retentive faecal incontinence